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141 results on '"D. D. Mulcahy"'

1. Low-frequency observations of the giant radio galaxy NGC 6251

Author: T. M. Cantwell, Marcus Brüggen, Aleksandar Shulevski, P. N. Best, Marek Jamrozy, Martin J. Hardcastle, C. L. Van Eck, Emanuela Orrú, D. D. Mulcahy, M. Iacobelli, Joseph R. Callingham, G. Brunetti, S. S. Sridhar, H. J. A. Röttgering, Justin D. Bray, Volker Heesen, Shane O'Sullivan, C. J. Riseley, R. Morganti, Jeremy J. Harwood, Anna M. M. Scaife, Judith H. Croston, George Heald, A. O. Clarke, Cyril Tasse, and Astronomy
Subjects: Physics, radio continuum: galaxies, polarization, 010308 nuclear & particles physics, Radio galaxy, galaxies: active, Extrapolation, FOS: Physical sciences, Astronomy and Astrophysics, polarisation, Astrophysics, LOFAR, Electron, Low frequency, Polarization (waves), Lambda, 01 natural sciences, Astrophysics - Astrophysics of Galaxies, galaxies [radio continuum], Spectral line, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), active [galaxies], 0103 physical sciences, 010303 astronomy & astrophysics
Abstract: We present LOFAR observations at 150 MHz of the borderline FRI/FRII giant radio galaxy NGC 6251. This paper presents the most sensitive and highest-resolution images of NGC 6251 at these frequencies to date, revealing for the first time a low-surface-brightness extension to the northern lobe, and a possible backflow associated with the southern lobe. The integrated spectra of components of NGC 6251 are consistent with previous measurements at higher frequencies, similar to results from other LOFAR studies of nearby radio galaxies. We find the outer structures of NGC 6251 to be either at equipartition or slightly electron dominated, similar to those of FRII sources rather than FRIs; but this conclusion remains tentative because of uncertainties associated with the geometry and the extrapolation of X-ray measurements to determine the external pressure distribution on the scale of the outer lobes. We place lower limits on the ages of the extension of the northern lobe and the backflow of the southern lobe of $t \gtrsim 250$ Myr and $t \gtrsim 210$ Myr respectively. We present the first detection of polarisation at 150 MHz in NGC 6251. Taking advantage of the high Faraday resolution of LOFAR, we place an upper limit on the magnetic field in the group of $B < 0.2 (\Lambda_B / 10 {\rm kpc})^{-0.5} \mu$G for a coherence scale of $\Lambda_B < 60 {\rm kpc}$ and $B < 13 \mu$G for $\Lambda_B = 240$ kpc., Comment: 19 pages, 17 figures; accepted by MNRAS
Published: 2020

2. Magnetic fields and cosmic rays in M 31. I. Spectral indices, scale lengths, Faraday rotation, and magnetic field pattern

Author: D. D. Mulcahy, R. Beck, Elly M. Berkhuijsen, and R. Gießübel
Subjects: J.2, Field (physics), FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, 010305 fluids & plasmas, law.invention, symbols.namesake, law, 0103 physical sciences, Faraday effect, Pitch angle, Faraday cage, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Physics, Astronomy and Astrophysics, Polarization (waves), Astrophysics - Astrophysics of Galaxies, Magnetic field, 85-05, Amplitude, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), symbols, Dynamo
Abstract: Three deep radio continuum surveys of the Andromeda galaxy, M 31, were performed at 11.3, 6.2, and 3.6 cm wavelength with the Effelsberg 100-m telescope. At all wavelengths, the total and polarized emission is concentrated in a ring-like structure between about 7 kpc and 13 kpc radius from the center. Propagation of cosmic rays away from star-forming regions is evident. The ring of synchrotron emission is wider than the ring of the thermal radio emission, and the radial scale length of synchrotron emission is larger than that of thermal emission. The polarized intensity from the ring varies double-periodically with azimuthal angle, indicating that the ordered magnetic field is almost oriented along the ring, with a pitch angle of -14{\deg} $\pm$ 2{\deg}. Faraday rotation measures (RM) show a large-scale sinusoidal variation with azimuthal angle, signature of an axisymmetric spiral (ASS) regular magnetic field, plus a superimposed double-periodic variation of a bisymmetric spiral (BSS) field with about 6x smaller amplitude. The dominating ASS field of M 31 is the most compelling case so far of a field generated by the action of a mean-field dynamo. The RM amplitude between 6.2 cm and 3.6 cm is about 50% larger than between 11.3 cm and 6.2 cm, indicating that Faraday depolarization at 11.3 cm is stronger than at 6.2 cm and 3.6 cm. The phase of the sinusoidal RM variation of -7{\deg} $\pm$ 1{\deg} is interpreted as the average spiral pitch angle of the regular field. The average pitch angle of the ordered field, as derived from the intrinsic orientation of the polarized emission (corrected for Faraday rotation), is significantly smaller: -26{\deg} $\pm$ 3{\deg}. The difference in pitch angle of the regular and the ordered fields indicates that the ordered field contains a significant fraction of an anisotropic turbulent field that has a different pattern than the regular (ASS + BSS) field., Comment: Accepted for publication in Astronomy 6 Astrophysics
Published: 2019

3. Radio haloes in nearby galaxies modelled with 1D cosmic ray transport using spinnaker

Author: Rainer Beck, D. D. Mulcahy, B. S. Koribalski, Tobias Westmeier, Marita Krause, Ettore Carretti, George Heald, Dominik J. Bomans, R. J. Dettmar, M. Dumke, B. Adebahr, Volker Heesen, and Judith A. Irwin
Subjects: Physics, Spectral index, 010308 nuclear & particles physics, Star formation, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astronomy and Astrophysics, Cosmic ray, Scale height, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Astrophysics - Astrophysics of Galaxies, 01 natural sciences, Galaxy, law.invention, Radio telescope, Telescope, Space and Planetary Science, law, Astrophysics of Galaxies (astro-ph.GA), 0103 physical sciences, Halo, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics
Abstract: We present radio continuum maps of 12 nearby ($D\leq 27~\rm Mpc$), edge-on ($i\geq 76^{\circ}$), late-type spiral galaxies mostly at $1.4$ and 5 GHz, observed with the Australia Telescope Compact Array, Very Large Array, Westerbork Synthesis Radio Telescope, Effelsberg 100-m and Parkes 64-m telescopes. All galaxies show clear evidence of radio haloes, including the first detection in the Magellanic-type galaxy NGC 55. In 11 galaxies, we find a thin and a thick disc that can be better fitted by exponential rather than Gaussian functions. We fit our SPINNAKER (SPectral INdex Numerical Analysis of K(c)osmic-ray Electron Radio-emission) 1D cosmic-ray transport models to the vertical model profiles of the non-thermal intensity and to the non-thermal radio spectral index in the halo. We simultaneously fit for the advection speed (or diffusion coefficient) and magnetic field scale height. In the thick disc, the magnetic field scale heights range from 2 to 8 kpc with an average across the sample of $3.0\pm 1.7~\rm kpc$; they show no correlation with either star-formation rate (SFR), SFR surface density ($\Sigma_{\rm SFR}$) or rotation speed ($V_{\rm rot}$). The advection speeds range from 100 to $700~\rm km\,s^{-1}$ and display correlations of $V\propto \rm SFR^{0.36\pm 0.06}$ and $V\propto \Sigma_{\rm SFR}^{0.39\pm 0.09}$; they agree remarkably well with the escape velocities ($0.5\leq V/V_{\rm esc}\leq 2$), which can be explained by cosmic-ray driven winds. Radio haloes show the presence of disc winds in galaxies with $\Sigma_{\rm SFR} > 10^{-3}~\rm M_{\odot}\,yr^{-1}\,kpc^{-2}$ that extend over several kpc and are driven by processes related to the distributed star formation in the disc., Comment: 39 pages, 20 colour figures, 10 tables. Accepted by MNRAS
Published: 2018

4. A large light-mass component of cosmic rays at 10(17)-10(17.5) electronvolts from radio observations

Author: Vishambhar Pandey, D. D. Mulcahy, M. A. Garrett, J. van Leeuwen, Tim Hassall, Adam Deller, Harvey Butcher, D. Engels, H. Paas, John Conway, J. E. Enriquez, A. I. F. Stewart, M. Pandey-Pommier, Matthias Steinmetz, Rob Fender, B. Ciardi, M. Pietka, E. Juette, G. van Diepen, P. N. Best, M. C. Toribio, A. Horneffer, Chiara Ferrari, M. P. van Haarlem, S. Duscha, Mark J. Bentum, Stefan J. Wijnholds, Jochen Eislöffel, Sarod Yatawatta, Emanuela Orrú, M. Kuniyoshi, Michael Kramer, Anna Nelles, C. Vogt, R. J. van Weeren, Martin Bell, Maaijke Mevius, John D. Swinbank, P. Maat, Matthias Hoeft, M. J. Norden, Pim Schellart, D. McKay-Bukowski, J. A. Zensus, John McKean, Dominik J. Schwarz, Richard Fallows, Aris Karastergiou, Ph. Zarka, V. I. Kondratiev, T. N. G. Trinh, Stijn Buitink, Heino Falcke, Michael W. Wise, Jörg P. Rachen, Benjamin Stappers, Jason W. T. Hessels, J. Sluman, Gianni Bernardi, Jörg R. Hörandel, I. M. Avruch, James M. Anderson, F. de Gasperin, Frank Breitling, Roberto Pizzo, H. J. A. Röttgering, Satyendra Thoudam, G. Kuper, Olaf Wucknitz, M. Serylak, H. Munk, Wilfred Frieswijk, Ashish Asgekar, Marcus Brüggen, M. Iacobelli, Y. Tang, W. Reich, S. ter Veen, A. W. Gunst, Anna M. M. Scaife, Laura Rossetto, Ralph A. M. J. Wijers, A. G. Polatidis, Rebecca McFadden, Arthur Corstanje, Annalisa Bonafede, Christian Vocks, G. M. Loose, Sera Markoff, Jean-Mathias Grießmeier, Michel Tagger, D. Carbone, R. C. Vermeulen, T. Huege, Olaf Scholten, Oleg Smirnov, Huib Intema, Cyril Tasse, J. W. Broderick, E. de Geus, R. J. Dettmar, George Heald, W. N. Brouw, Gottfried Mann, High Energy Astrophys. & Astropart. Phys (API, FNWI), Radboud University [Nijmegen], Netherlands Institute for Radio Astronomy (ASTRON), Karlsruhe Institute of Technology (KIT), University of Groningen [Groningen], Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Laboratoire Analyse, Géométrie et Applications (LAGA), Université Paris 8 Vincennes-Saint-Denis (UP8)-Université Paris 13 (UP13)-Institut Galilée-Centre National de la Recherche Scientifique (CNRS), Institute for Mathematics Applied to Geoscience, National Center for Atmospheric Research [Boulder] (NCAR), SRON Netherlands Institute for Space Research (SRON), Australia Telescope National Facility (ATNF), Commonwealth Scientific and Industrial Research Organisation [Canberra] (CSIRO), University of Edinburgh, Jacobs University [Bremen], Leibniz-Institut für Astrophysik Potsdam (AIP), University of Southampton, Kapteyn Astronomical Institute [Groningen], University of Amsterdam [Amsterdam] (UvA), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Onsala Space Observatory, Dept. of Radio and Space Science, Chalmers University of Technology, Chalmers University of Technology [Göteborg], Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), Medstar Research Institute, Astronomisches Institut der Ruhr-Universität Bochum, Ruhr-Universität Bochum [Bochum], Thüringer Landessternwarte Tautenburg (TLS), SETI Institute, Institute of Mathematical and Physical Sciences, Département de Géologie, Université de Montréal (UdeM), Leiden Observatory [Leiden], Universiteit Leiden, Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], Max-Planck-Institut für Radioastronomie (MPIFR), Oxford Astrophysics, University of Oxford, Columbia Astrophysics Laboratory (CAL), Columbia University [New York], Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Oulu, Center for Information Technology CIT, Université de Groningen, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), National Radio Astronomy Observatory [Charlottesville] (NRAO), National Radio Astronomy Observatory (NRAO), School of Physics and Astronomy [Southampton], Interactions Son Musique Mouvement, Sciences et Technologies de la Musique et du Son (STMS), Institut de Recherche et Coordination Acoustique/Musique (IRCAM)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche et Coordination Acoustique/Musique (IRCAM)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Rhodes University, Grahamstown, Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH / Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures (DSMZ), Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Université Paris-Sud - Paris 11 (UP11), SKA South Africa, Ska South Africa, Galaxies, Etoiles, Physique, Instrumentation (GEPI), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Finca El Encin, Instituto Madrileño de Investigación y Desarrollo Rural, Agrario y Alimentario (IMIDRA), Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, Observatoire de Paris - Site de Paris (OP), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, European Project: 227610,EC:FP7:ERC,ERC-2008-AdG,LOFAR-AUGER(2009), European Project: 640130,H2020,ERC-2014-STG,LOFAR(2015), Radboud university [Nijmegen], Institute for Nuclear Physics (IKP), Karlsruhe Institute of Technology, nstitute for Nuclear Physics (IKP), Karlsruhe Institute of Technology, Université Paris 8 Vincennes-Saint-Denis (UP8)-Centre National de la Recherche Scientifique (CNRS)-Institut Galilée-Université Paris 13 (UP13), Universiteit Leiden [Leiden], Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), University of Oxford [Oxford], École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Research unit Astroparticle Physics, Astronomy, and Kapteyn Astronomical Institute
Subjects: TELESCOPE, High-energy astronomy, Astronomy, Astrophysics::High Energy Astrophysical Phenomena, Cosmic ray, Astrophysics, Electron, Astrophysics::Cosmology and Extragalactic Astrophysics, Radiation, EXTENSIVE AIR-SHOWERS, 01 natural sciences, 0103 physical sciences, 010303 astronomy & astrophysics, Astroparticle physics, Physics, Multidisciplinary, COSMIC cancer database, 010308 nuclear & particles physics, Astrophysics::Instrumentation and Methods for Astrophysics, LOFAR, ENERGY-SPECTRUM, SIMULATIONS, PULSES, High-energy astrophysics, Air shower, 13. Climate action, [SDU]Sciences of the Universe [physics], ARRAY, Neutrino, Particle astrophysics, EMISSION
Abstract: Cosmic rays are the highest-energy particles found in nature. Measurements of the mass composition of cosmic rays with energies of 1017–1018 electronvolts are essential to understanding whether they have galactic or extragalactic sources. It has also been proposed that the astrophysical neutrino signal1 comes from accelerators capable of producing cosmic rays of these energies2. Cosmic rays initiate air showers—cascades of secondary particles in the atmosphere—and their masses can be inferred from measurements of the atmospheric depth of the shower maximum3 (Xmax; the depth of the air shower when it contains the most particles) or of the composition of shower particles reaching the ground4. Current measurements5 have either high uncertainty, or a low duty cycle and a high energy threshold. Radio detection of cosmic rays6,7,8 is a rapidly developing technique9 for determining Xmax (refs 10, 11) with a duty cycle of, in principle, nearly 100 per cent. The radiation is generated by the separation of relativistic electrons and positrons in the geomagnetic field and a negative charge excess in the shower front6,12. Here we report radio measurements of Xmax with a mean uncertainty of 16 grams per square centimetre for air showers initiated by cosmic rays with energies of 1017–1017.5 electronvolts. This high resolution in Xmax enables us to determine the mass spectrum of the cosmic rays: we find a mixed composition, with a light-mass fraction (protons and helium nuclei) of about 80 per cent. Unless, contrary to current expectations, the extragalactic component of cosmic rays contributes substantially to the total flux below 1017.5 electronvolts, our measurements indicate the existence of an additional galactic component, to account for the light composition that we measured in the 1017–1017.5 electronvolt range.
Published: 2019

5. Reliable detection and characterization of low-frequency polarized sources in the LOFAR M51 field

Author: Stephen Bourke, D. D. Mulcahy, A. Neld, A. Horneffer, Andrew Fletcher, John Conway, Krzysztof T. Chyzy, C. L. Van Eck, George Heald, Błażej Nikiel-Wroczyński, Cathy Horellou, Tobia Carozzi, S. S. Sridhar, Jamie Farnes, Marijke Haverkorn, R. Beck, Rosita Paladino, and Astronomy
Subjects: RADIO-SOURCES, individual: M51 [galaxies], Astronomy, FOS: Physical sciences, GALAXY M51, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, DETECTION THRESHOLDS, 01 natural sciences, law.invention, REIONIZATION WINDOWS, symbols.namesake, Optics, magnetic fields [galaxies], law, polarimetric [techniques], 0103 physical sciences, Faraday effect, data analysis [methods], Faraday cage, 010303 astronomy & astrophysics, radio continuum: galaxies, Physics, polarization, LINEAR-POLARIZATION, Line-of-sight, 010308 nuclear & particles physics, business.industry, Linear polarization, MAGNETIC-FIELD, Astronomy and Astrophysics, LOFAR, FARADAY-ROTATION, Polarization (waves), methods: data analysis, Astrophysics - Astrophysics of Galaxies, galaxies [radio continuum], Square degree, techniques: polarimetric, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), galaxies: individual: M51, symbols, MILKY-WAY, Radio frequency, galaxies: magnetic fields, business, ROTATION MEASURE SYNTHESIS, FALSE-DISCOVERY RATE
Abstract: The new generation of broad-band radio continuum surveys will provide large data sets with polarization information. New algorithms need to be developed to extract reliable catalogs of linearly polarized sources that can be used to characterize those sources and produce a dense rotation measure (RM) grid to probe magneto-ionized structures along the line of sight via Faraday rotation. The aim of the paper is to develop a computationally efficient and rigorously defined source-finding algorithm for linearly polarized sources. We used a calibrated data set from the LOw Frequency ARray (LOFAR) at 150 MHz centered on the nearby galaxy M51 to search for polarized background sources. With a new imaging software, we re-imaged the field at a resolution of 18''x15'' and cataloged a total of about 3000 continuum sources within 2.5 degrees of the center of M51. We made small Stokes Q and U images centered on each source brighter than 100 mJy in total intensity (201 sources) and used RM synthesis to create corresponding Faraday cubes that were analyzed individually. For each source, the noise distribution function was determined from a subset of measurements at high Faraday depths where no polarization is expected; the peaks in polarized intensity in the Faraday spectrum were identified and the p-value of each source was calculated. Finally, the false discovery rate method was applied to the list of p-values to produce a list of polarized sources and quantify the reliability of the detections. We also analyzed sources fainter than 100 mJy but that were reported as polarized in the literature at at least another radio frequency. Of the 201 sources that were searched for polarization, 6 polarized sources were detected confidently (with a false discovery rate of 5 percent). This corresponds to a number density of 1 polarized source per 3.3 square degrees, or 0.3 source/square degree. [Abridged], 17 pages, 11 figures, accepted for publication in A&A
Published: 2018

6. Investigation of the cosmic ray population and magnetic field strength in the halo of NGC 891

Author: Nima Razavi-Ghods, Keith Grainge, S. S. Sridhar, D. D. Mulcahy, Paul F. Scott, Błażej Nikiel-Wroczyński, Philip Schmidt, Aritra Basu, George Heald, Y. Perrot, A. Horneffer, Fatemeh Tabatabaei, Anna M. M. Scaife, Marita Krause, Rainer Beck, R. J. Dettmar, M. Iacobelli, Cathy Horellou, Rosita Paladino, David Titterington, Marijke Haverkorn, Richard G. Strom, T. M. Cantwell, J. Hickish, Volker Heesen, Krzysztof T. Chyzy, S. H. Carey, and Astronomy
Subjects: J.2, Arcminute Microkelvin Imager, Astronomy, galaxies: halos, Astrophysics, magnetic fields, GALACTIC WIND, 01 natural sciences, magnetic fields [galaxies], galaxies, individual, EDGE-ON GALAXIES, 010303 astronomy & astrophysics, Physics, Spectral index, education.field_of_study, magnetic fields / cosmic rays / radio continuum, NGC 891 / galaxies, halos [galaxies], Spectral energy distribution, Halo, galaxies: magnetic fields, galaxies: ISM, ARCMINUTE MICROKELVIN IMAGER, Astrophysics::High Energy Astrophysical Phenomena, Population, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, cosmic rays, RADIO-CONTINUUM OBSERVATIONS, SPIRAL GALAXY NGC-891, 0103 physical sciences, galaxies: individual: NGC 891, STAR-FORMING GALAXIES, NEARBY GALAXIES, education, Astrophysics::Galaxy Astrophysics, radio continuum: galaxies, Spiral galaxy, ISM [galaxies], INTERSTELLAR-MEDIUM, 010308 nuclear & particles physics, halos / galaxies, Astronomy and Astrophysics, Astrophysics - Astrophysics of Galaxies, Galaxy, galaxies [radio continuum], ISM / galaxies, Interstellar medium, 85-05, SPECTRAL ENERGY-DISTRIBUTION, Space and Planetary Science, individual: NGC 891 [galaxies], Astrophysics of Galaxies (astro-ph.GA), X-RAY
Abstract: Low-frequency radio continuum observations of edge-on galaxies are ideal to study cosmic-ray electrons (CREs) in halos via radio synchrotron emission and to measure magnetic field strengths. We obtained new observations of the edge-on spiral galaxy NGC 891 at 129-163 MHz with the LOw Frequency ARray (LOFAR) and at 13-18 GHz with the Arcminute Microkelvin Imager (AMI) and combine them with recent high-resolution Very Large Array (VLA) observations at 1-2 GHz, enabling us to study the radio continuum emission over two orders of magnitude in frequency. The spectrum of the integrated nonthermal flux density can be fitted by a power law with a spectral steepening towards higher frequencies or by a curved polynomial. Spectral flattening at low frequencies due to free-free absorption is detected in star-forming regions of the disk. The mean magnetic field strength in the halo is 7 +- 2 $\mu$G. The scale heights of the nonthermal halo emission at 146 MHz are larger than those at 1.5 GHz everywhere, with a mean ratio of 1.7 +- 0.3, indicating that spectral ageing of CREs is important and that diffusive propagation dominates. The halo scale heights at 146 MHz decrease with increasing magnetic field strengths which is a signature of dominating synchrotron losses of CREs. On the other hand, the spectral index between 146 MHz and 1.5 GHz linearly steepens from the disk to the halo, indicating that advection rather than diffusion is the dominating CRE transport process. This issue calls for refined modelling of CRE propagation., Comment: Accepted for publication in Astronomy & Astrophysics
Published: 2018

7. LOFAR MSSS: Flattening low-frequency radio continuum spectra of nearby galaxies

Author: Adam Stewart, Jamie Farnes, B. Adebahr, R. J. van Weeren, M. Pandey-Pommier, Joseph R. Callingham, C. J. Riseley, Antonia Rowlinson, Aleksandar Shulevski, Volker Heesen, K. Sendlinger, Huub Röttgering, George Heald, A. J. van der Horst, Emanuela Orru, P. Surma, Anna M. M. Scaife, R.-J. Dettmar, M. Curyło, Rene P. Breton, D. D. Mulcahy, J. Piotrowska, Martin J. Hardcastle, Rainer Beck, S. S. Sridhar, Rosita Paladino, R. Pizzo, Marco Iacobelli, A. O. Clarke, Błażej Nikiel-Wroczyński, W. Jurusik, J. W. Broderick, V. Vacca, Krzysztof T. Chyzy, G. Gürkan, Natalia Nowak, V. N. Pandey, John Conway, High Energy Astrophys. & Astropart. Phys (API, FNWI), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), and Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: media_common.quotation_subject, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Cosmic ray, Astrophysics, galaxies [Radio continuum], Astrophysics::Cosmology and Extragalactic Astrophysics, Low frequency, 01 natural sciences, Flattening, Spectral line, statistics [Galaxies], 0103 physical sciences, 010306 general physics, 010303 astronomy & astrophysics, galaxies: statistics, Astrophysics::Galaxy Astrophysics, media_common, Physics, radio continuum: galaxies, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Astronomy and Astrophysics, LOFAR, Viewing angle, evolution [Galaxies], Astrophysics - Astrophysics of Galaxies, Galaxy, Space and Planetary Science, Sky, [SDU]Sciences of the Universe [physics], Astrophysics of Galaxies (astro-ph.GA), galaxies: evolution
Abstract: The shape of low-frequency radio continuum spectra of normal galaxies is not well understood, the key question being the role of physical processes such as thermal absorption in shaping them. In this work we take advantage of the LOFAR Multifrequency Snapshot Sky Survey (MSSS) to investigate such spectra for a large sample of nearby star-forming galaxies. Using the measured 150MHz flux densities from the LOFAR MSSS survey and literature flux densities at various frequencies we have obtained integrated radio spectra for 106 galaxies. The spectra are explained through the use of a three-dimensional model of galaxy radio emission, and radiation transfer dependent on the galaxy viewing angle and absorption processes. Spectra of our galaxies are generally flatter at lower compared to higher frequencies but as there is no tendency for the highly inclined galaxies to have more flattened low-frequency spectra, we argue that the observed flattening is not due to thermal absorption, contradicting the suggestion of Israel & Mahoney (1990). According to our modelled radio maps for M51-like galaxies, the free-free absorption effects can be seen only below 30MHz and in the global spectra just below 20MHz, while in the spectra of starburst galaxies, like M82, the flattening due to absorption is instead visible up to higher frequencies of about 150MHz. Locally, within galactic disks, the absorption effects are distinctly visible in M51-like galaxies as spectral flattening around 100-200MHz in the face-on objects, and as turnovers in the edge-on ones, while in M82-like galaxies there are strong turnovers at frequencies above 700MHz, regardless of viewing angle. Our modelling suggests that the weak spectral flattening observed in the nearby galaxies studied here results principally from synchrotron spectral curvature due to cosmic ray energy losses and propagation effects., Accepted for publication in Astronomy and Astrophysics (corrected typo in the title)
Published: 2018

8. Source finding in linear polarization for LOFAR, and SKA predecessor surveys, using Faraday moments

Author: H. Junklewitz, C. L. Van Eck, A. Horneffer, D. D. Mulcahy, Michiel A. Brentjens, Jamie Farnes, Marijke Haverkorn, C. J. Riseley, Rosita Paladino, Valentina Vacca, Cathy Horellou, D.I. Jones, and George Heald
Subjects: media_common.quotation_subject, Astronomy, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Standard deviation, law.invention, Radio telescope, law, 0103 physical sciences, Faraday cage, 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries), media_common, Physics, 010308 nuclear & particles physics, Linear polarization, Bandwidth (signal processing), Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, LOFAR, Polarization (waves), Space and Planetary Science, Sky, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: The optimal source-finding strategy for linear polarization data is an unsolved problem, with many inhibitive factors imposed by the technically-challenging nature of polarization observations. Such an algorithm is essential for Square Kilometre Array (SKA) pathfinder surveys, such as the Multifrequency Snapshot Sky Survey (MSSS) with the LOw Frequency ARray (LOFAR), as data volumes are significant enough to prohibit manual inspection. We present a new strategy of `Faraday Moments' for source-finding in linear polarization with LOFAR, using the moments of the frequency-dependent full-Stokes data (i.e. the mean, standard deviation, skewness, and excess kurtosis). Through simulations of the sky, we find that moments can identify polarized sources with a high completeness: 98.5% at a signal-to-noise of 5. While the method has low reliability, Rotation Measure (RM) Synthesis can be applied per candidate source to filter out instrumental and spurious detections. This combined strategy will result in a complete and reliable catalogue of polarized sources that includes the full sensitivity of the observational bandwidth. We find that the technique can reduce the number of pixels on which RM Synthesis needs to be performed by a factor of $\approx1\times10^{5}$ for source distributions anticipated with modern radio telescopes. Through tests on LOFAR data, we find that the technique works effectively in the presence of diffuse emission. Extensions of this method are directly applicable to other upcoming radio surveys such as the POlarization Sky Survey of the Universe's Magnetism (POSSUM) with the Australia Square Kilometre Array Pathfinder (ASKAP), and the SKA itself., Accepted for publication in MNRAS
Published: 2017

9. The association of a J-burst with a solar jet

Author: Helmut O. Rucker, Rebecca McFadden, B. Ciardi, J. M. Anderson, H. Munk, J. W. Broderick, O. Wucknitz, H. Paas, E. Juette, W. Reich, Heino Falcke, Matthias Hoeft, Hamish A. S. Reid, Oleg Smirnov, L. Cerrigone, A. G. Polatidis, Philip Best, Emanuela Orrú, Matthias Steinmetz, J. Magdalenic, D. D. Mulcahy, Gottfried Mann, C. Vocks, P. Zarka, V. N. Pandey, Ashish Asgekar, Mark J. Bentum, Gerard H. Kuper, A. Nelles, Annalisa Bonafede, M. Iacobelli, Diana E. Morosan, Dominik J. Schwarz, M. Pandey-Pommier, M. C. Toribio, R. C. Vermeulen, Jochen Eislöffel, Jean-Mathias Griessmeier, M. Tagger, S. ter Veen, A. W. Gunst, S. Duscha, Mario M. Bisi, R. Blaauw, R. J. van Weeren, D. McKay-Bukowski, I. M. Avruch, Peter T. Gallagher, John McKean, Martin Bell, E. de Geus, M. A. Garrett, Richard Fallows, Frank Breitling, Bo Thidé, J. Sluman, Roberto Pizzo, Marcus Brüggen, Satyendra Thoudam, Astronomy, Kapteyn Astronomical Institute, Trinity College Dublin, Netherlands Institute for Radio Astronomy (ASTRON), SUPA School of Physics and Astronomy [Glasgow], University of Glasgow, Leibniz-Institut für Astrophysik Potsdam (AIP), STFC Rutherford Appleton Laboratory (RAL), Science and Technology Facilities Council (STFC), Royal Observatory of Belgium [Brussels] (ROB), Austrian Academy of Sciences (OeAW), Swedish Institute of Space Physics [Uppsala] (IRF), GeoForschungsZentrum - Helmholtz-Zentrum Potsdam (GFZ), Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], CSIRO Astronomy and Space Science, Commonwealth Scientific and Industrial Research Organisation [Canberra] (CSIRO), Royal Observatory Edinburgh (ROE), University of Edinburgh, Jacobs University [Bremen], Universität Hamburg (UHH), Max-Planck-Institut für Astrophysik (MPA), Max-Planck-Gesellschaft, Thüringer Landessternwarte Tautenburg (TLS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Leiden Observatory [Leiden], Universiteit Leiden, Ruhr-Universität Bochum [Bochum], University of Oulu, Radboud University [Nijmegen], Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Max-Planck-Institut für Radioastronomie (MPIFR), Universität Bielefeld, Rhodes University, Grahamstown, Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH / Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures (DSMZ), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University-Smithsonian Institution, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO), Universiteit Leiden [Leiden], Radboud university [Nijmegen], École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), and Harvard University [Cambridge]-Smithsonian Institution
Subjects: corona [Sun], 010504 meteorology & atmospheric sciences, Astronomy, particle emission [Sun], Astrophysics, 01 natural sciences, ELECTRON-BEAMS, CORONA, Sun: magnetic, Coronal mass ejection, Astrophysics::Solar and Stellar Astrophysics, GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries), 010303 astronomy & astrophysics, Sun: magnetic fields, fields, Physics, Jet (fluid), Solar flare, Sun: radio radiation, Astrophysics::Instrumentation and Methods for Astrophysics, FLARE, Astrophysics - Solar and Stellar Astrophysics, magnetic fields [Sun], Physical Sciences, Physics::Space Physics, Astrophysics::Earth and Planetary Astrophysics, FLUX, DYNAMICS-OBSERVATORY SDO, Field line, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astronomy & Astrophysics, ACCELERATION, Computer Science::Digital Libraries, III BURSTS, Sun: particle emission, 0103 physical sciences, Solar and Stellar Astrophysics (astro-ph.SR), 0105 earth and related environmental sciences, Science & Technology, radio radiation [Sun], [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Sun: corona, Northern Hemisphere, Astronomy and Astrophysics, Magnetic reconnection, LOFAR, Physics::History of Physics, X-RAY JETS, 13. Climate action, Space and Planetary Science, Extreme ultraviolet, RADIO-EMISSION
Abstract: Context. The Sun is an active star that produces large-scale energetic events such as solar flares and coronal mass ejections and numerous smaller-scale events such as solar jets. These events are often associated with accelerated particles that can cause emission at radio wavelengths. The reconfiguration of the solar magnetic field in the corona is believed to be the cause of the majority of solar energetic events and accelerated particles. Aims. Here, we investigate a bright J-burst that was associated with a solar jet and the possible emission mechanism causing these two phenomena. Methods. We used data from the Solar Dynamics Observatory (SDO) to observe a solar jet, and radio data from the Low Frequency Array (LOFAR) and the Nan\c{c}ay Radioheliograph (NRH) to observe a J-burst over a broad frequency range (33-173 MHz) on 9 July 2013 at ~11:06 UT. Results. The J-burst showed fundamental and harmonic components and it was associated with a solar jet observed at extreme ultraviolet wavelengths with SDO. The solar jet occurred at a time and location coincident with the radio burst, in the northern hemisphere, and not inside a group of complex active regions in the southern hemisphere. The jet occurred in the negative polarity region of an area of bipolar plage. Newly emerged positive flux in this region appeared to be the trigger of the jet. Conclusions. Magnetic reconnection between the overlying coronal field lines and the newly emerged positive field lines is most likely the cause of the solar jet. Radio imaging provides a clear association between the jet and the J-burst which shows the path of the accelerated electrons., Comment: 11 pages, 8 figures
Published: 2017

10. LOFAR discovery of a quiet emission mode in PSR B0823+26

Author: F. Breitling, Gottfried Mann, R. Pizzo, John D. Anderson, Cees Bassa, Sera Markoff, Rene P. Breton, Ashish Asgekar, Charlotte Sobey, E. Jütte, George Heald, Heino Falcke, P. Maat, M. J. Norden, M. A. Garrett, Jean-Mathias Grießmeier, Ph. Zarka, Rebecca McFadden, H. Paas, Ben Stappers, E. de Geus, Sarod Yatawatta, V. I. Kondratiev, D. D. Mulcahy, J. van Leeuwen, S. ter Veen, M. Pilia, M. Pandey-Pommier, Ralph A. M. J. Wijers, A. W. Gunst, J. Sluman, Olaf Wucknitz, H. J. A. Röttgering, Philip Best, Christian Vocks, D. McKay-Bukowski, Michel Tagger, D. Carbone, A. Alexov, Andrew Lyne, Antonia Rowlinson, A. Noutsos, Adam Stewart, Chiara Ferrari, T. E. Hassall, Evan Keane, Patrick Weltevrede, Jason W. T. Hessels, Satyendra Thoudam, S. Duscha, M. Serylak, A. van Duin, G. Pietka, Laura Birzan, Jochen Eislöffel, J. P. Hamaker, Wilfred Frieswijk, C. Toribio, Michael Kramer, D. A. Rafferty, A. G. Polatidis, Arthur Corstanje, A. Nelles, John D. Swinbank, Y. Tang, Anna M. M. Scaife, Martin Bell, N. J. Young, V. N. Pandey, Gerard H. Kuper, Cyril Tasse, J. W. Broderick, H. Munk, John McKean, Marcus Brüggen, Matthias Steinmetz, Annalisa Bonafede, A. Renting, Richard Fallows, R. Vermeulen, Mark J. Bentum, Matthias Hoeft, M. de Vos, Aris Karastergiou, Michael W. Wise, Gianni Bernardi, Jörg R. Hörandel, Rob Fender, Oleg Smirnov, Emanuela Orru, Dominik J. Schwarz, I. M. Avruch, Anna V. Bilous, R. J. van Weeren, Sobey, C., Young, N.J., Hessels, J.W.T., Weltevrede, P., Noutsos, A., Stappers, B.W., Kramer, M., Bassa, C., Lyne, A.G., Kondratiev V.I., null, Hassall, T.E., Keane, E.F., Bilous, A.V., Breton, R.P., Grießmeier, J.M., Karastergiou, A., Pilia, M., Serylak, M., Ter Veen, S., Van Leeuwen, J., Alexov, A., Anderson, J., Asgekar, A., Avruch, I.M., Bell, M.E., Bentum, M.J., Bernardi, G., Best, P., Bĭrzan, L., Bonafede, A., Breitling, F., Broderick, J., Brüggen, M., Corstanje, A., Carbone, D., De Geus, E., De Vos, M., Van Duin, A., Duscha, S., Eislöffel, J., Falcke, H., Fallows, R.A., Fender, R., Ferrari, C., Frieswijk, W., Garrett, M.A., Gunst, A.W., Hamaker, J.P., Heald, G., Hoeft, M., Hörandel, J., Jütte, E., Kuper, G., Maat, P., Mann, G., Markoff, S., McFadden, R., McKay-Bukowski, D., McKean, J.P., Mulcahy, D.D., Munk, H., Nelles, A., Norden, M.J., Orrù, E., Paas, H., Pandey-Pommier, M., Pandey, V.N., Pietka, G., Pizzo, R., Polatidis, A.G., Rafferty, D., Renting, A., Röttgering, H., Rowlinson, A., Scaife, A.M.M., Schwarz, D., Sluman, J., Smirnov, O., Steinmetz, M., Stewart, A., Swinbank, J., Tagger, M., Tang, Y., Tasse, C., Thoudam, S., Toribio, C., Vermeulen, R., Vocks, C., Van Weeren, R.J., Wijers, R.A.M.J., Wise, M.W., Wucknitz, O., Yatawatta, S., Zarka, P., Max-Planck-Institut für Radioastronomie (MPIFR), University of Minnesota [Twin Cities] (UMN), University of Minnesota System, University of Amsterdam [Amsterdam] (UvA), Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], Columbia Astrophysics Laboratory (CAL), Columbia University [New York], Cornell University [New York], Netherlands Institute for Radio Astronomy (ASTRON), Centre for Astrophysics and Supercomputing [Swinburne] (CAS), Swinburne University of Technology [Melbourne], Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Radboud University [Nijmegen], Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Rhodes University, Grahamstown, Oxford Astrophysics, University of Oxford, Institute for Mathematics Applied to Geoscience, National Center for Atmospheric Research [Boulder] (NCAR), SRON Netherlands Institute for Space Research (SRON), CSIRO Astronomy and Space Science, Commonwealth Scientific and Industrial Research Organisation [Canberra] (CSIRO), Laboratoire de Physique Nucléaire et de Hautes Énergies (LPNHE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), University of Edinburgh, Leiden Observatory [Leiden], Universiteit Leiden, Jacobs University [Bremen], Leibniz-Institut für Astrophysik Potsdam (AIP), University of Southampton, Medstar Research Institute, Thüringer Landessternwarte Tautenburg (TLS), Institute of Mathematical and Physical Sciences, Département de Géologie, Université de Montréal (UdeM), University Bochum, Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Oulu, Center for Information Technology CIT, Université de Groningen, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), National Radio Astronomy Observatory [Charlottesville] (NRAO), National Radio Astronomy Observatory (NRAO), Department of Astronomy and Astrophysics [PennState], Pennsylvania State University (Penn State), Penn State System-Penn State System, School of Physics and Astronomy [Southampton], Interactions Son Musique Mouvement, Sciences et Technologies de la Musique et du Son (STMS), Institut de Recherche et Coordination Acoustique/Musique (IRCAM)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche et Coordination Acoustique/Musique (IRCAM)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH / Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures (DSMZ), Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Université Paris-Sud - Paris 11 (UP11), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), SKA South Africa, Ska South Africa, Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University-Smithsonian Institution, Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, We would like to thank R. Karuppusamy for his help with the Effelsberg observations. CF acknowledges financial support by the Agence Nationale de la Recherche through grant ANR-09-JCJC-0001-01., European Project: 337062,EC:FP7:ERC,ERC-2013-StG,DRAGNET(2014), ITA, GBR, FRA, DEU, NLD, Radboud university [Nijmegen], Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO), University of Oxford [Oxford], Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Pierre et Marie Curie - Paris 6 (UPMC), Universiteit Leiden [Leiden], École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Harvard University [Cambridge]-Smithsonian Institution, Astronomy, and High Energy Astrophys. & Astropart. Phys (API, FNWI)
Subjects: stars, PSR B0823+26-radio telescopes, Astronomy, Astrophysics::High Energy Astrophysical Phenomena, Pulsar planet, FOS: Physical sciences, neutron- pulsars, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, neutron [stars], Pulsar, Millisecond pulsar, Pulsars: individual: PSR B0823+26, individual, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Astroparticle physics, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, LOFAR, Astronomy and Astrophysic, Stars: neutron, Stars, Neutron star, Astrophysics - Solar and Stellar Astrophysics, magnetosphere-pulsars, [SDU]Sciences of the Universe [physics], Space and Planetary Science, QUIET, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, Astrophysics - High Energy Astrophysical Phenomena, individual: PSR B0823+26 [pulsars]
Abstract: PSR B0823+26, a 0.53-s radio pulsar, displays a host of emission phenomena over timescales of seconds to (at least) hours, including nulling, subpulse drifting, and mode-changing. Studying pulsars like PSR B0823+26 provides further insight into the relationship between these various emission phenomena and what they might teach us about pulsar magnetospheres. Here we report on the LOFAR discovery that PSR B0823+26 has a weak and sporadically emitting 'quiet' (Q) emission mode that is over 100 times weaker (on average) and has a nulling fraction forty-times greater than that of the more regularly-emitting 'bright' (B) mode. Previously, the pulsar has been undetected in the Q-mode, and was assumed to be nulling continuously. PSR B0823+26 shows a further decrease in average flux just before the transition into the B-mode, and perhaps truly turns off completely at these times. Furthermore, simultaneous observations taken with the LOFAR, Westerbork, Lovell, and Effelsberg telescopes between 110 MHz and 2.7 GHz demonstrate that the transition between the Q-mode and B-mode occurs within one single rotation of the neutron star, and that it is concurrent across the range of frequencies observed., Comment: 15 pages, 8 figures, 2 tables, accepted for publication in MNRAS
Published: 2015

11. LOFAR MSSS: Discovery of a 2.56 Mpc giant radio galaxy associated with a disturbed galaxy group

Author: Michael W. Wise, Leah K. Morabito, Jeremy J. Harwood, D. Carbone, Emanuela Orru, T. M. Cantwell, Judith H. Croston, Marisa Brienza, G. Kokotanekov, Rosita Paladino, George Heald, D. D. Mulcahy, A. O. Clarke, Annalisa Bonafede, A. Horneffer, Luke Pratley, Huub Röttgering, Martin J. Hardcastle, Adam Stewart, S. S. Sridhar, Cyril Tasse, Marco Iacobelli, R. Pizzo, J. W. Broderick, Jamie Farnes, A. J. van der Horst, K. Sendlinger, Anna M. M. Scaife, Rene P. Breton, J. Sabater, Volker Heesen, Thomas H. Jarrett, W. Jurusik, M. Pietka, Justin D. Bray, S. van Velzen, Błażej Nikiel-Wroczyński, John McKean, M. Pandey-Pommier, Antonia Rowlinson, R. J. van Weeren, C. J. Riseley, Aleksandar Shulevski, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Centre de Recherche Astrophysique de Lyon ( CRAL ), École normale supérieure - Lyon ( ENS Lyon ) -Université Claude Bernard Lyon 1 ( UCBL ), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ), Galaxies, Etoiles, Physique, Instrumentation ( GEPI ), Institut national des sciences de l'Univers ( INSU - CNRS ) -Observatoire de Paris-Université Paris Diderot - Paris 7 ( UPD7 ) -Centre National de la Recherche Scientifique ( CNRS ), Astronomy, Kapteyn Astronomical Institute, Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), and High Energy Astrophys. & Astropart. Phys (API, FNWI)
Subjects: SELECTION, Active galactic nucleus, Cosmology and Nongalactic Astrophysics (astro-ph.CO), Stellar mass, Radio galaxy, Astronomy, [ PHYS.ASTR ] Physics [physics]/Astrophysics [astro-ph], Astrophysics::High Energy Astrophysical Phenomena, UNIVERSE, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, galaxies [infrared], infrared: galaxies, surveys, galaxies: groups: general, Galaxy group, 0103 physical sciences, WISE, galaxies: interactions, FIELD, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Physics, radio continuum: galaxies, 010308 nuclear & particles physics, Star formation, groups: general [galaxies], interactions [galaxies], supermassive black holes [quasars], quasars: supermassive black holes, Velocity dispersion, Astronomy and Astrophysics, LOFAR, ATLAS, Astrophysics - Astrophysics of Galaxies, Galaxy, galaxies [radio continuum], EVOLUTION, I. SURVEY DESCRIPTION, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), ALL-SKY SURVEY, SDSS-III, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, CLUSTERS, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: We report on the discovery in the LOFAR Multifrequency Snapshot Sky Survey (MSSS) of a giant radio galaxy (GRG) with a projected size of $2.56 \pm 0.07$ Mpc projected on the sky. It is associated with the galaxy triplet UGC 9555, within which one is identified as a broad-line galaxy in the Sloan Digital Sky Survey (SDSS) at a redshift of $0.05453 \pm 1 \times 10^{-5} $, and with a velocity dispersion of $215.86 \pm 6.34$ km/s. From archival radio observations we see that this galaxy hosts a compact flat-spectrum radio source, and we conclude that it is the active galactic nucleus (AGN) responsible for generating the radio lobes. The radio luminosity distribution of the jets, and the broad-line classification of the host AGN, indicate this GRG is orientated well out of the plane of the sky, making its physical size one of the largest known for any GRG. Analysis of the infrared data suggests that the host is a lenticular type galaxy with a large stellar mass ($\log~\mathrm{M}/\mathrm{M}_\odot = 11.56 \pm 0.12$), and a moderate star formation rate ($1.2 \pm 0.3~\mathrm{M}_\odot/\mathrm{year}$). Spatially smoothing the SDSS images shows the system around UGC 9555 to be significantly disturbed, with a prominent extension to the south-east. Overall, the evidence suggests this host galaxy has undergone one or more recent moderate merger events and is also experiencing tidal interactions with surrounding galaxies, which have caused the star formation and provided the supply of gas to trigger and fuel the Mpc-scale radio lobes., Compressed for arXiv, see journal for full resolution images
Published: 2017

12. LOFAR MSSS: The Scaling Relation between AGN Cavity Power and Radio Luminosity at Low Radio Frequencies

Author: D. D. Mulcahy, Michael W. Wise, Aleksandar Shulevski, Marco Iacobelli, M. Pandey-Pommier, Antonia Rowlinson, George Heald, G. Gürkan, Adam Stewart, Jeremy J. Harwood, Emanuela Orru, Błażej Nikiel-Wroczyński, C. J. Riseley, Anna M. M. Scaife, John McKean, Leith Godfrey, R. Pizzo, M. de Vries, Huib Intema, Cyril Tasse, J. W. Broderick, G. Kokotanekov, Chiara Ferrari, D. A. Rafferty, D. Carbone, V. N. Pandey, Judith H. Croston, Huub Röttgering, Luke Pratley, A. O. Clarke, Laura Birzan, Annalisa Bonafede, A. J. van der Horst, Rene P. Breton, R. J. van Weeren, W. Jurusik, Martin J. Hardcastle, S. S. Sridhar, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Astronomy, Centre de Recherche Astrophysique de Lyon ( CRAL ), École normale supérieure - Lyon ( ENS Lyon ) -Université Claude Bernard Lyon 1 ( UCBL ), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ), Galaxies, Etoiles, Physique, Instrumentation ( GEPI ), Institut national des sciences de l'Univers ( INSU - CNRS ) -Observatoire de Paris-Université Paris Diderot - Paris 7 ( UPD7 ) -Centre National de la Recherche Scientifique ( CNRS ), Joseph Louis LAGRANGE ( LAGRANGE ), Université Nice Sophia Antipolis ( UNS ), Université Côte d'Azur ( UCA ) -Université Côte d'Azur ( UCA ) -Observatoire de la Côte d'Azur, Université Côte d'Azur ( UCA ) -Centre National de la Recherche Scientifique ( CNRS ), High Energy Astrophys. & Astropart. Phys (API, FNWI), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, and Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: clusters: individual: MS 0735.6+7421 [galaxies], Astronomy, [ PHYS.ASTR ] Physics [physics]/Astrophysics [astro-ph], Astrophysics, galaxies: clusters: individual: Perseus, 01 natural sciences, galaxies: clusters: individual: 2A 0335+096, law.invention, law, HYDRA-A, 010303 astronomy & astrophysics, media_common, Physics, MAGNETIC-FIELD, galaxies: clusters: individual: MS 0735.6+7421, clusters: individual: A2199 [galaxies], clusters: intracluster medium [galaxies], ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, Radio frequency, INTRACLUSTER MEDIUM, galaxies: clusters: individual: A2199, Astrophysics - Cosmology and Nongalactic Astrophysics, Cosmology and Nongalactic Astrophysics (astro-ph.CO), PERSEUS CLUSTER, galaxies: clusters: intracluster medium, GASEOUS ATMOSPHERE, media_common.quotation_subject, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, clusters: individual: 2A 0335+096 [galaxies], clusters: individual: Perseus [galaxies], Astrophysics::Cosmology and Extragalactic Astrophysics, Low frequency, RAY-EMITTING GAS, 0103 physical sciences, Cluster (physics), Scaling, Astrophysics::Galaxy Astrophysics, VLA OBSERVATIONS, 010308 nuclear & particles physics, Bolometer, JET-POWER, Astronomy and Astrophysics, LOFAR, Astrophysics - Astrophysics of Galaxies, Galaxy, Space and Planetary Science, Sky, Astrophysics of Galaxies (astro-ph.GA), X-rays: galaxies: clusters, galaxies: clusters [X-rays], GALAXY CLUSTERS, SKY SURVEY, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: International audience; We present a new analysis of the widely used relation between cavity power and radio luminosity in clusters of galaxies with evidence for strong AGN feedback. We studied the correlation at low radio frequencies using two new surveys – the first alternative data release of the TIFR GMRT Sky Survey (TGSS ADR1) at 148 MHz and LOFAR’s firstall-sky survey, the Multifrequency Snapshot Sky Survey (MSSS) at 140 MHz. We find a scaling relation Pcav ∝ Lβ148, with a logarithmic slope of β = 0.51 ± 0.14, which is in good agreement with previous results based on data at 327 MHz. The large scatter present in this correlation confirms the conclusion reached at higher frequencies that the total radio luminosity at a single frequency is a poor predictor of the total jet power. Previous studies have shown that the magnitude of this scatter can be reduced when bolometric radio luminosity corrected for spectral aging is used. We show that including additional measurements at 148 MHz alone is insufficient to improve this correction and further reduce the scatter in the correlation. For a subset of four well-resolved sources, we examined the detected extended structures at low frequencies and compare with the morphology known from higher frequency images and Chandra X-ray maps. In the case of Perseus we discuss details in the structures of the radio mini-halo, while in the 2A 0335+096 cluster we observe new diffuse emission associated with multiple X-ray cavities and likely originating from past activity. For A2199 and MS 0735.6+7421, we confirm that the observed low-frequency radio lobes are confined to the extents known from higher frequencies. This new low-frequency analysis highlights the fact that existing cavity power to radio luminosity relations are based on a relatively narrow range of AGN outburst ages. We discuss how the correlation could be extended using low frequency data from the LOFAR Two-metre Sky Survey (LoTSS) in combination with future, complementary deeper X-ray observations. Key words: galaxies: clusters: individual: 2A 0335+096 / galaxies: clusters: individual: Perseus / X-rays: galaxies: clusters / galaxies: clusters: individual: A2199 / galaxies: clusters: individual: MS 0735.6+7421 / galaxies: clusters: intracluster medium
Published: 2017

13. LOFAR imaging of Cygnus A - direct detection of a turnover in the hotspot radio spectra

Author: Aris Karastergiou, Michael W. Wise, Gianni Bernardi, Heino Falcke, L. Cerrigone, D. Engels, Michel Tagger, Simona Vegetti, Anna Nelles, R. Morganti, John D. Swinbank, Leith Godfrey, George Heald, I. van Bemmel, E. Juette, P. Maat, Sera Markoff, V. I. Kondratiev, Léon V. E. Koopmans, Huib Intema, Adam Deller, H. Munk, J. W. Broderick, Marcus Brüggen, R. Blaauw, J. Sluman, M. Iacobelli, R. J. van Weeren, Roberto Pizzo, Philip Best, A. J. van der Horst, D. McKay-Bukowski, Wilfred Frieswijk, M. Pandey-Pommier, Martin J. Hardcastle, M. Pietka, Aleksandar Shulevski, Rainer Beck, Satyendra Thoudam, M. Serylak, Matthias Steinmetz, Anna M. M. Scaife, Emanuela Orrú, Antonia Rowlinson, D. D. Mulcahy, Sarod Yatawatta, H. Paas, Adam Stewart, S. Duscha, I. M. Avruch, Frank Breitling, B. Ciardi, John McKean, H. J. A. Röttgering, R. C. Vermeulen, Oleg Smirnov, Olaf Wucknitz, W. Reich, Gottfried Mann, F. de Gasperin, P. Zarka, M. Kuniyoshi, D. Rafferty, Martin Bell, Richard Fallows, James M. Anderson, G. Kuper, Mark J. Bentum, M. A. Garrett, J.-M. Grießmeier, Matthias Hoeft, Christian Vocks, M. P. van Haarlem, M. C. Toribio, A. G. Polatidis, J. van Leeuwen, Annalisa Bonafede, Rebecca McFadden, Netherlands Institute for Radio Astronomy (ASTRON), SRON Netherlands Institute for Space Research (SRON), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), University of Hertfordshire [Hatfield] (UH), Department of Astronomy and Astrophysics [PennState], Pennsylvania State University (Penn State), Penn State System-Penn State System, Department of Atmospheric and Planetary Sciences [Hampton] (APS), Hampton University, Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Université de Tours (UT), CSIRO Astronomy and Space Science, Commonwealth Scientific and Industrial Research Organisation [Canberra] (CSIRO), University of Southampton, Laboratoire de Physique Nucléaire et de Hautes Énergies (LPNHE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), University of Edinburgh, Jacobs University [Bremen], Leibniz-Institut für Astrophysik Potsdam (AIP), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Radboud University [Nijmegen], Institute of Mathematical and Physical Sciences, Leiden Observatory [Leiden], Universiteit Leiden, Unité Scientifique de la Station de Nançay (USN), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Joint Institute for VLBI in Europe (JIVE ERIC), Department of Pure Mathematics and Mathematical Statistics (DPMMS), Faculty of mathematics Centre for Mathematical Sciences [Cambridge] (CMS), University of Cambridge [UK] (CAM)-University of Cambridge [UK] (CAM), Ruhr-Universität Bochum [Bochum], Oxford Astrophysics, University of Oxford, Max-Planck-Institut für Radioastronomie (MPIFR), University of Oulu, University of Groningen, Groningen, Netherlands, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Australia Telescope National Facility (ATNF), School of Physics and Astronomy [Southampton], Department of Physics and Astronomy [South Africa], University of the Western Cape (UWC), Rhodes University, Grahamstown, Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH / Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures (DSMZ), Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University-Smithsonian Institution, Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), European Project: 320745,EC:FP7:ERC,ERC-2012-ADG_20120216,RADIOLIFE(2013), Astronomy, McKean, J.P., Godfrey, L.E.H., Vegetti, S., Wise, M.W., Morganti, R., Hardcastle, M.J., Rafferty, D., Anderson, J., Avruch, I.M., Beck, R., Bell, M.E., van Bemmel, I., Bentum, M.J., Bernardi, G., Best, P., Blaauw, R., Bonafede, A., Breitling, F., Broderick, J.W., Brüggen, M., Cerrigone, L., Ciardi, B., de Gasperin, F., Deller, A., Duscha, S., Engels, D., Falcke, H., Fallows, R.A., Frieswijk, W., Garrett, M.A., Grießmeier, J.M., van Haarlem, M.P., Heald, G., Hoeft, M., van der HorstA.J., null, Iacobelli, M., Interna, H., Juette, E., Karastergiou, A., Kondratiev, V.I., Koopmans, L.V.E., Kuniyoshi, M., Kuper, G., van Leeuwen, J., Maat, P., Mann, G., Markoff, S., McFadden, R., McKay-Bukowski, D., Mulcahy, D.D., Munk, H., Nelles, A., Orru, E., Paas, H., Pandey-Pommier, M., Pietka, M., Pizzo, R., Polatidis, A.G., Reich, W., Rottgering, H.J.A., Rowlinson, A., Scaife, A.M.M., Serylak, M., Shulevski, A., Sluman, J., Smirnov, O., Steinmetz, M., Stewart, A., Swinbank, J., Tagger, M., Thoudam, S., Toribio, M.C., Vermeulen, R., Vocks, C., van Weeren, R.J., Wucknitz, O., Yatawatta, S., Zarka, P., High Energy Astrophys. & Astropart. Phys (API, FNWI), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Pierre et Marie Curie - Paris 6 (UPMC), Radboud university [Nijmegen], Universiteit Leiden [Leiden], Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), University of Oxford [Oxford], École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), University of the Western Cape, Smithsonian Institution-Harvard University [Cambridge], ITA, GBR, FRA, DEU, NLD, Université de Tours, Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National d’Études Spatiales [Paris] (CNES), and Harvard University [Cambridge]-Smithsonian Institution
Subjects: Radio galaxy, Astronomy, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Radio continuum: galaxie, Spectral line, Radio spectrum, Radio continuum: galaxies, Galaxies: active: individual: Cygnus A, X-shaped radio galaxy, 0103 physical sciences, Cygnus A, 010303 astronomy & astrophysics, Physics, Spectral index, EWI-27659, 010308 nuclear & particles physics, LOBES, Astronomy and Astrophysics, LOFAR, Astronomy and Astrophysic, Astrophysics - Astrophysics of Galaxies, Galaxy, galaxies [radio continuum], GALAXIES, METIS-321690, RESOLUTION, Space and Planetary Science, HOT-SPOTS, GAS, [SDU]Sciences of the Universe [physics], Astrophysics of Galaxies (astro-ph.GA), ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, ARRAY, IR-103274
Abstract: The low-frequency radio spectra of the hotspots within powerful radio galaxies can provide valuable information about the physical processes operating at the site of the jet termination. These processes are responsible for the dissipation of jet kinetic energy, particle acceleration, and magnetic-field generation. Here we report new observations of the powerful radio galaxy Cygnus A using the Low Frequency Array (LOFAR) between 109 and 183 MHz, at an angular resolution of ~3.5 arcsec. The radio emission of the lobes is found to have a complex spectral index distribution, with a spectral steepening found towards the centre of the source. For the first time, a turnover in the radio spectrum of the two main hotspots of Cygnus A has been directly observed. By combining our LOFAR imaging with data from the Very Large Array at higher frequencies, we show that the very rapid turnover in the hotspot spectra cannot be explained by a low-energy cut-off in the electron energy distribution, as has been previously suggested. Thermal (free-free) absorption or synchrotron self absorption models are able to describe the low-frequency spectral shape of the hotspots, however, as with previous studies, we find that the implied model parameters are unlikely, and interpreting the spectra of the hotspots remains problematic., Comment: 9 pages, 3 figures, accepted for publication in MNRAS
Published: 2016

14. Corrigendum: A large light-mass component of cosmic rays at 10

Author: S, Buitink, A, Corstanje, H, Falcke, J R, Hörandel, T, Huege, A, Nelles, J P, Rachen, L, Rossetto, P, Schellart, O, Scholten, S, Ter Veen, S, Thoudam, T N G, Trinh, J, Anderson, A, Asgekar, I M, Avruch, M E, Bell, M J, Bentum, G, Bernardi, P, Best, A, Bonafede, F, Breitling, J W, Broderick, W N, Brouw, M, Brüggen, H R, Butcher, D, Carbone, B, Ciardi, J E, Conway, F, de Gasperin, E, de Geus, A, Deller, R-J, Dettmar, G, van Diepen, S, Duscha, J, Eislöffel, D, Engels, J E, Enriquez, R A, Fallows, R, Fender, C, Ferrari, W, Frieswijk, M A, Garrett, J M, Grießmeier, A W, Gunst, M P, van Haarlem, T E, Hassall, G, Heald, J W T, Hessels, M, Hoeft, A, Horneffer, M, Iacobelli, H, Intema, E, Juette, A, Karastergiou, V I, Kondratiev, M, Kramer, M, Kuniyoshi, G, Kuper, J, van Leeuwen, G M, Loose, P, Maat, G, Mann, S, Markoff, R, McFadden, D, McKay-Bukowski, J P, McKean, M, Mevius, D D, Mulcahy, H, Munk, M J, Norden, E, Orru, H, Paas, M, Pandey-Pommier, V N, Pandey, M, Pietka, R, Pizzo, A G, Polatidis, W, Reich, H J A, Röttgering, A M M, Scaife, D J, Schwarz, M, Serylak, J, Sluman, O, Smirnov, B W, Stappers, M, Steinmetz, A, Stewart, J, Swinbank, M, Tagger, Y, Tang, C, Tasse, M C, Toribio, R, Vermeulen, C, Vocks, C, Vogt, R J, van Weeren, R A M J, Wijers, S J, Wijnholds, M W, Wise, O, Wucknitz, S, Yatawatta, P, Zarka, and J A, Zensus
Published: 2016

15. Modelling the cosmic ray electron propagation in M 51

Author: Dipanjan Mitra, D. D. Mulcahy, Anna M. M. Scaife, Andrew Fletcher, and Rainer Beck
Subjects: Milky Way, FOS: Physical sciences, Cosmic ray, galaxies [Radio continuum], Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, law.invention, Radio telescope, law, Polarization, ISM [Galaxies], 0103 physical sciences, Cosmic rays, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Physics, Spectral index, 010308 nuclear & particles physics, Star formation, magnetic fields [Galaxies], Astronomy and Astrophysics, Astrophysics - Astrophysics of Galaxies, Galaxy, Synchrotron, Interstellar medium, individual: M 51 [Galaxies], Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA)
Abstract: Cosmic ray electrons (CREs) are a crucial part of the ISM and are observed via synchrotron emission. While much modelling has been carried out on the CRE distribution and propagation of the Milky Way, little has been done on normal external star-forming galaxies. Recent spectral data from a new generation of radio telescopes enable us to find more robust estimations of the CRE propagation. We model the synchrotron spectral index of M 51 using the time-dependent diffusion energy-loss equation and to compare the model results with the observed spectral index determined from recent low-frequency observations with LOFAR. This is the first time that this model for CRE propagation has been solved for a realistic distribution of CRE sources, which we derive from the observed star formation rate, in an external galaxy. The radial variation of the synchrotron spectral index and scale-length produced by the model are compared to recent LOFAR and older VLA observational data and also to new observations of M 51 at 325MHz obtained with the GMRT. We find that propagation of CREs by diffusion alone is sufficient to reproduce the observed spectral index distribution in M 51. An isotropic diffusion coefficient with a value of $6.6\pm0.2\,\times 10^{28}\mathrm{cm}^2\,\mathrm{s}^{-1}$ is found to fit best and is similar to what is seen in the Milky Way. We estimate an escape time of $11\,\mathrm{Myr}$ from the central galaxy to $88\,\mathrm{Myr}$ in the extended disk. It is found that an energy dependence of the diffusion coefficient is not important for CRE energies in the range $0.01\,\mathrm{GeV}$--$3\,\mathrm{GeV}$. We are able to reproduce the dependence of the observed synchrotron scale-lengths on frequency, with $l \propto \nu^{-1/4}$ in the outer disk and $l \propto \nu^{-1/8}$ in the inner disk., Comment: 15 pages, 21 figures, accepted for publication in A&A
Published: 2016

16. LBCS: The LOFAR Long-Baseline Calibrator Survey

Author: Rebecca McFadden, G. M. Loose, J. van Leeuwen, J. Schaap, N. J. Vermaas, M. P. van Haarlem, Philip Best, M. Sipior, E. de Geus, E. Juette, D. Engels, Sarod Yatawatta, J. Moldón, George Heald, Anna M. M. Scaife, C. Vocks, F. Breitling, M. Iacobelli, L. Cerrigone, D. D. Mulcahy, H. J. A. Röttgering, Matthias Hoeft, John D. Swinbank, Jean-Mathias Griessmeier, W. Reich, P. Maat, James M. Anderson, M. A. Garrett, Amitpal S. Tagore, I. van Bemmel, J. Sluman, Roberto Pizzo, R. Vermeulen, Marcus Brüggen, Satyendra Thoudam, Aleksandar Shulevski, R. Blaauw, M. C. Toribio, Emanuela Orrú, A. Horneffer, R. J. van Weeren, W. N. Brouw, Martin Bell, M. Avruch, Michael W. Wise, Jörg R. Hörandel, D. McKay-Bukowski, Jochen Eislöffel, Gerard H. Kuper, P. Zarka, Adam Deller, A. Drabent, Mark J. Bentum, Arthur Corstanje, Dominik J. Schwarz, Matthias Steinmetz, F. de Gasperin, Richard Fallows, H. Munk, A. G. Polatidis, Tobia Carozzi, Annalisa Bonafede, S. ter Veen, Leah K. Morabito, A. W. Gunst, John Conway, Anna D. Kapińska, Huib Intema, Heino Falcke, J. W. Broderick, M. Pandey-Pommier, Neal Jackson, Antonia Rowlinson, John McKean, Michiel A. Brentjens, B. Ciardi, Eskil Varenius, O. Wucknitz, M. Kuniyoshi, School of Physics and Astronomy [Manchester], University of Manchester [Manchester], Netherlands Institute for Radio Astronomy (ASTRON), Departament d'Astronomia i Meteorologia [Barcelona], Universitat de Barcelona (UB), Onsala Space Observatory, Dept. of Radio and Space Science, Chalmers University of Technology, Chalmers University of Technology [Göteborg], ARC Centre of Excellence for Autonomous Systems (CAS), University of Technology Sydney (UTS), Swedish Institute of Space Physics [Uppsala] (IRF), Department of Pure Mathematics and Mathematical Statistics (DPMMS), Faculty of mathematics Centre for Mathematical Sciences [Cambridge] (CMS), University of Cambridge [UK] (CAM)-University of Cambridge [UK] (CAM), Department of Astrophysics [Nijmegen], Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Radboud university [Nijmegen]-Radboud university [Nijmegen], GeoForschungsZentrum - Helmholtz-Zentrum Potsdam (GFZ), Newcastle University [Newcastle], Joint Institute for VLBI in Europe (JIVE ERIC), University of Hamburg, Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Leibniz-Institut für Astrophysik Potsdam (AIP), Oxford Astrophysics, University of Oxford [Oxford], University of Southampton, Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], University of Edinburgh, Radboud university [Nijmegen], Thüringer Landessternwarte Tautenburg (TLS), Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Max-Planck-Institut für Radioastronomie (MPIFR), Astronomisches Institut der Ruhr-Universität Bochum, Ruhr-Universität Bochum [Bochum], National Astronomical Observatory of Japan (NAOJ), Health Service Executive [Dublin] (HSE), Aalborg University [Denmark] (AAU), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Astrophysikalisches Institut Potsdam (AIP), Princeton University, SRON Netherlands Institute for Space Research (SRON), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), European Project: 283393,EC:FP7:INFRA,FP7-INFRASTRUCTURES-2011-1,RADIONET3(2012), High Energy Astrophys. & Astropart. Phys (API, FNWI), Radboud University [Nijmegen]-Radboud University [Nijmegen], Universiteit Leiden, University of Oxford, Radboud University [Nijmegen], Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Jackson, N., Tagore, A., Deller, A., Moldón, J., Varenius, E., Morabito, L., Wucknitz, O., Carozzi, T., Conway, J., Drabent, A., Kapinska, A., Orrù, E., Brentjens, M., Blaauw, R., Kuper, G., Sluman, J., Schaap, J., Vermaas, N., Iacobelli, M., Cerrigone, L., Shulevski, A., Ter Veen, S., Fallows, R., Pizzo, R., Sipior, M., Anderson, J., Avruch, I.M., Bell, M.E., Van Bemmel, I., Bentum, M.J., Best, P., Bonafede, A., Breitling, F., Broderick, J.W., Brouw, W.N., Brüggen, M., Ciardi, B., Corstanje, A., De Gasperin, F., De Geus, E., Eislöffel, J., Engels, D., Falcke, H., Garrett, M.A., Grießmeier, J.M., Gunst, A.W., Van Haarlem, M.P., Heald, G., Hoeft, M., Hörandel, J., Horneffer, A., Intema, H., Juette, E., Kuniyoshi, M., Van Leeuwen, J., Loose, G.M., Maat, P., McFadden, R., McKay-Bukowski, D., McKean, J.P., Mulcahy, D.D., Munk, H., Pandey-Pommier, M., Polatidis, A.G., Reich, W., Röttgering, H.J.A., Rowlinson, A., Scaife, A.M.M., Schwarz, D.J., Steinmetz, M., Swinbank, J., Thoudam, S., Toribio, M.C., Vermeulen, R., Vocks, C., Van Weeren, R.J., Wise, M.W., Yatawatta, S., Zarka, P., and Astronomy
Subjects: Coherence time, media_common.quotation_subject, Astronomy, interferometers [instrumentation], galaxies: active, EWI-27445, Flux, FOS: Physical sciences, 02 engineering and technology, 01 natural sciences, Radio continuum: galaxie, law.invention, Instrumentation: interferometer, Telescope, surveys, law, 0103 physical sciences, 0202 electrical engineering, electronic engineering, information engineering, Range (statistics), Astronomy, Astrophysics and Cosmology, Survey, instrumentation: interferometers, 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries), media_common, radio continuum: galaxies, Instrumentation:interferometers- Techniques:interferometric - Surveys - Galaxies:active -Radio continuum:galaxies, 020206 networking & telecommunications, Astronomy and Astrophysics, LOFAR, Astronomy and Astrophysic, Geodesy, Astrophysics - Astrophysics of Galaxies, galaxies [radio continuum], Square degree, interferometric [techniques], METIS-319490, Sky, Space and Planetary Science, techniques: interferometric, [SDU]Sciences of the Universe [physics], Astrophysics of Galaxies (astro-ph.GA), active [galaxies], Environmental science, Astrophysics - Instrumentation and Methods for Astrophysics, IR-102283, Coherence (physics)
Abstract: (abridged). We outline LBCS (the LOFAR Long-Baseline Calibrator Survey), whose aim is to identify sources suitable for calibrating the highest-resolution observations made with the International LOFAR Telescope, which include baselines >1000 km. Suitable sources must contain significant correlated flux density (50-100mJy) at frequencies around 110--190~MHz on scales of a few hundred mas. At least for the 200--300-km international baselines, we find around 1 suitable calibrator source per square degree over a large part of the northern sky, in agreement with previous work. This should allow a randomly selected target to be successfully phase calibrated on the international baselines in over 50% of cases. Products of the survey include calibrator source lists and fringe-rate and delay maps of wide areas -- typically a few degrees -- around each source. The density of sources with significant correlated flux declines noticeably with baseline length over the range 200--600~km, with good calibrators on the longest baselines appearing only at the rate of 0.5 per square degree. Coherence times decrease from 1--3 minutes on 200-km baselines to about 1 minute on 600-km baselines, suggesting that ionospheric phase variations contain components with scales of a few hundred kilometres. The longest median coherence time, at just over 3 minutes, is seen on the DE609 baseline, which at 227km is close to being the shortest. We see median coherence times of between 80 and 110 seconds on the four longest baselines (580--600~km), and about 2 minutes for the other baselines. The success of phase transfer from calibrator to target is shown to be influenced by distance, in a manner that suggests a coherence patch at 150-MHz of the order of 1 degree., Accepted by Astronomy & Astrophysics. Error in figure 6 corrected
Published: 2016

17. LOFAR MSSS: detection of a low-frequency radio transient in 400 h of monitoring of the North Celestial Pole

Author: Rebecca McFadden, Martin Bell, Sera Markoff, G. Kokotanekov, R. J. van Weeren, D. McKay-Bukowski, James M. Anderson, Jason W. T. Hessels, Peter G. Jonker, Ralph A. M. J. Wijers, H. Munk, Casey J. Law, Frank Breitling, B. Scheers, Marcus Brüggen, M. C. Toribio, A. Horneffer, George Heald, M. A. Garrett, Aris Karastergiou, Luke Pratley, Rudy Wijnands, Y. Cendes, F. de Gasperin, A. Alexov, Michael W. Wise, Gianni Bernardi, Jörg R. Hörandel, B. Ciardi, M. Kuniyoshi, James Miller-Jones, J. van Leeuwen, T. Munoz-Darias, Aleksandar Shulevski, John McKean, J.-M. Grießmeier, John D. Swinbank, Jochen Eislöffel, P. Maat, Cyril Tasse, Wilfred Frieswijk, M. J. Norden, J. W. Broderick, A. G. Polatidis, Arthur Corstanje, T E Hassall, Heino Falcke, Harvey Butcher, E. de Geus, V. I. Kondratiev, E. Juette, Anna M. M. Scaife, M. Pandey-Pommier, Benjamin Stappers, H. Paas, A. W. Gunst, I. M. Avruch, Volker Heesen, D. Carbone, Mark J. Bentum, Antonia Rowlinson, Annalisa Bonafede, Rob Fender, J. Sluman, E. Rol, Matthias Steinmetz, Chiara Ferrari, Gijs Molenaar, S. Duscha, G. Kuper, D. D. Mulcahy, Sarod Yatawatta, Philip Best, M. Pietka, H. J. A. Röttgering, Satyendra Thoudam, A. O. Clarke, Adam Stewart, M. P. van Haarlem, Charlotte Sobey, M. Iacobelli, Olaf Wucknitz, Matthias Hoeft, Emanuela Orrú, M. Loose, Ph. Zarka, Adam Deller, Martin J. Hardcastle, Tim D. Staley, Ashish Asgekar, J. Moldon, Dominik J. Schwarz, A. J. van der Horst, Christian Vocks, Rene P. Breton, John Conway, Stephane Corbel, R. C. Vermeulen, Stefan J. Wijnholds, S. van Velzen, T. L. Grobler, Oleg Smirnov, Astronomy, Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], University of Southampton, Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], School of Physics and Astronomy [Southampton], Netherlands Institute for Radio Astronomy (ASTRON), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Oxford Astrophysics, University of Oxford [Oxford], Rhodes University, Grahamstown, CSIRO Astronomy and Space Science, Commonwealth Scientific and Industrial Research Organisation [Canberra] (CSIRO), Jacobs University [Bremen], Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Unité Scientifique de la Station de Nançay (USN), Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Universität Hamburg (UHH), Thüringer Landessternwarte Tautenburg (TLS), Radboud university [Nijmegen], Département de Géologie, Université de Montréal [Montréal], Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), University of Hertfordshire [Hatfield] (UH), Max-Planck-Institut für Radioastronomie (MPIFR), Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Curtin University [Perth], Planning and Transport Research Centre (PATREC), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Victoria University of Wellington, Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], SKA South Africa, Ska South Africa, Galaxies, Etoiles, Physique, Instrumentation (GEPI), PSL Research University (PSL)-PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Department of Mathematics, The George Washington University, Washington State University (WSU), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University [Cambridge]-Smithsonian Institution, Anton Pannekoek Institute for Astronomy, Observatoire de Paris - Site de Paris (OP), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Institute for Mathematics Applied to Geoscience, National Center for Atmospheric Research [Boulder] (NCAR), SRON Netherlands Institute for Space Research (SRON), Laboratoire de Physique Nucléaire et de Hautes Énergies (LPNHE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), University of Edinburgh, Leibniz-Institut für Astrophysik Potsdam (AIP), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Onsala Space Observatory, Dept. of Radio and Space Science, Chalmers University of Technology, Chalmers University of Technology [Göteborg], Ruhr-Universität Bochum [Bochum], University of Oulu, The Netherlands Institute for Radio Astronomy (ASTRON), 7990-AA Dwingeloo, Netherlands, Departament d'Astronomia i Meteorologia [Barcelona], Institut de Ciènces del Cosmos (ICC), Universitat de Barcelona (UB)-Universitat de Barcelona (UB), Center for Information Technology CIT, Université de Groningen, Interactions Son Musique Mouvement, Sciences et Technologies de la Musique et du Son (STMS), Université Pierre et Marie Curie - Paris 6 (UPMC)-IRCAM-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-IRCAM-Centre National de la Recherche Scientifique (CNRS), Rhodes University, Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH / Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures (DSMZ), Finca El Encin, Instituto Madrileño de Investigación y Desarrollo Rural, Agrario y Alimentario (IMIDRA), Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, High Energy Astrophys. & Astropart. Phys (API, FNWI), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO), Université de Montréal (UdeM), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Department of Mathematics [George Washington University] (GW), The George Washington University (GW), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Pierre et Marie Curie - Paris 6 (UPMC), Universitat de Barcelona (UB), Institut de Recherche et Coordination Acoustique/Musique (IRCAM)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche et Coordination Acoustique/Musique (IRCAM)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), University of Oxford, Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Radboud University [Nijmegen], Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Universiteit Leiden, École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Harvard University-Smithsonian Institution, Stewart, A.J., Fender, R.P., Broderick, J.W., Hassall, T.E., Muñoz-Darias, T., Rowlinson, A., Swinbank, J.D., Staley, T.D., Molenaar, G.J., Scheers, B., Grobler, T.L., Pietka, M., Heald, G., McKean, J.P., Bell, M.E., Bonafede, A., Breton, R.P., Carbone, D., Cendes, Y., Clarke, A.O., Corbel, S., De Gasperin, F., Eislöffel, J., Falcke, H., Ferrari, C., Grießmeier, J.-M., Hardcastle, M.J., Heesen, V., Hessels, J.W.T., Horneffer, A., Iacobelli, M., Jonker, P., Karastergiou, A., Kokotanekov, G., Kondratiev, V.I., Kuniyoshi, M., Law, C.J., van Leeuwen, J., Markoff, S., Miller-Jones, J.C.A., Mulcahy, D., Orru, E., Pandey-Pommier, M., Pratley, L., Rol, E., Röttgering, H.J.A., Scaife, A.M.M., Shulevski, A., Sobey, C.A., Stappers, B.W., Tasse, C., van der Horst, A.J., van Velzen, S., van Weeren, R.J., Wijers, R.A.M.J., Wijnands, R., Wise, M., Zarka, P., Alexov, A., Anderson, J., Asgekar, A., Avruch, I.M., Bentum, M.J., Bernardi, G., Best, P., Breitling, F., Brüggen, M., Butcher, H.R., Ciardi, B., Conway, J.E., Corstanje, A., de Geus, E., Deller, A., Duscha, S., Frieswijk, W., Garrett, M.A., Gunst, A.W., Van Haarlem, M.P., Hoeft, M., Hörandel, J., Juette, E., Kuper, G., Loose, M., Maat, P., McFadden, R., McKay-Bukowski, D., Moldon, J., Munk, H., Norden, M.J., Paas, H., Polatidis, A.G., Schwarz, D., Sluman, J., Smirnov, O., Steinmetz, M., Thoudam, S., Toribio, M.C., Vermeulen, R., Vocks, C., Wijnholds, S.J., Wucknitz, O., Yatawatta, S., ITA, GBR, FRA, DEU, and NLD
Subjects: Astronomy, media_common.quotation_subject, interferometers [instrumentation], radio continuum: general, FOS: Physical sciences, techniques: image processing, 02 engineering and technology, Astrophysics, Low frequency, 01 natural sciences, Instrumentation: interferometer, Celestial pole, 0103 physical sciences, IR-102656, 0202 electrical engineering, electronic engineering, information engineering, instrumentation: interferometers, Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, media_common, EWI-27481, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, image processing [techniques], METIS-320906, 020206 networking & telecommunications, Astronomy and Astrophysics, LOFAR, Limiting, Astronomy and Astrophysic, instrumentation: interferometers – techniques: image processing – radio continuum: general, radio, continuum: general, Observation duration, Space and Planetary Science, Sky, [SDU]Sciences of the Universe [physics], ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, general [radio continuum], Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: We present the results of a four-month campaign searching for low-frequency radio transients near the North Celestial Pole with the Low-Frequency Array (LOFAR), as part of the Multifrequency Snapshot Sky Survey (MSSS). The data were recorded between 2011 December and 2012 April and comprised 2149 11-minute snapshots, each covering 175 deg^2. We have found one convincing candidate astrophysical transient, with a duration of a few minutes and a flux density at 60 MHz of 15-25 Jy. The transient does not repeat and has no obvious optical or high-energy counterpart, as a result of which its nature is unclear. The detection of this event implies a transient rate at 60 MHz of 3.9 (+14.7, -3.7) x 10^-4 day^-1 deg^-2, and a transient surface density of 1.5 x 10^-5 deg^-2, at a 7.9-Jy limiting flux density and ~10-minute time-scale. The campaign data were also searched for transients at a range of other time-scales, from 0.5 to 297 min, which allowed us to place a range of limits on transient rates at 60 MHz as a function of observation duration., 23 pages, 16 figures, 5 tables, accepted for publication in MNRAS
Published: 2016

18. Discovery of a low-luminosity spiral DRAGN

Author: Y. Tawara, Ikuyuki Mitsuishi, Minnie Mao, Hiroshi Kobayashi, D. D. Mulcahy, Yasunori Babazaki, Hironori Matsumoto, Anna M. M. Scaife, A. O. Clarke, and R. Suganuma
Subjects: Physics, Giant Metrewave Radio Telescope, Spiral galaxy, 010308 nuclear & particles physics, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics - Astrophysics of Galaxies, 01 natural sciences, Galaxy, Luminosity, Space and Planetary Science, Bulge, Astrophysics of Galaxies (astro-ph.GA), 0103 physical sciences, Elliptical galaxy, Galaxy formation and evolution, 010303 astronomy & astrophysics, Spiral, Astrophysics::Galaxy Astrophysics
Abstract: Standard galaxy formation models predict that large-scale double-lobed radio sources, known as DRAGNs, will always be hosted by elliptical galaxies. In spite of this, in recent years a small number of spiral galaxies have also been found to host such sources. These so-called spiral DRAGNs are still extremely rare, with only $\sim 5$ cases being widely accepted. Here we report on the serendipitous discovery of a new spiral DRAGN in data from the Giant Metrewave Radio Telescope (GMRT) at 322 MHz. The host galaxy, MCG+07-47-10, is a face-on late-type Sbc galaxy with distinctive spiral arms and prominent bulge suggesting a high black hole mass. Using WISE infra-red and GALEX UV data we show that this galaxy has a star formation rate of 0.16-0.75 M$_{\odot}$yr$^{-1}$, and that the radio luminosity is dominated by star-formation. We demonstrate that this spiral DRAGN has similar environmental properties to others of this class, but has a comparatively low radio luminosity of $L_{\rm 1.4GHz}$ = 1.12$\times$10$^{22}$ W Hz$^{-1}$, two orders of magnitude smaller than other known spiral DRAGNs. We suggest that this may indicate the existence of a previously unknown low-luminosity population of spiral DRAGNS., 4 pages, Accepted for publication in Astronomy and Astrophysics
Published: 2016

19. Faraday tomography of the local interstellar medium with LOFAR: Galactic foregrounds towards IC342

Author: Charlotte Sobey, Anna M. M. Scaife, M. I. R. Alves, Vibor Jelić, M. Iacobelli, Cathy Horellou, D. D. Mulcahy, Torsten A. Enßlin, H. J. A. Röttgering, Ivan Marti-Vidal, D. H. F. M. Schnitzeler, W. Reich, Ron Beck, George Heald, A. G. de Bruyn, A. Horneffer, M. Haverkorn, S. S. Sridhar, Jamie Farnes, K. Ferrière, C. L. Van Eck, Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), and Astronomy
Subjects: Astronomy, DUST, Astrophysics, 01 natural sciences, ISM: clouds, law.invention, MHZ, law, Polarization, DEPOLARIZATION, Faraday cage, 010303 astronomy & astrophysics, Physics, Line-of-sight, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], ISM: magnetic fields, polarization, local insterstellar matter, radio continuum: ISM, Magnetic field, WIDE-FIELD, symbols, clouds [ISM], RADIO-SOURCES, Local insterstellar matter, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Radio telescope, symbols.namesake, 0103 physical sciences, Faraday effect, BUBBLE, Astrophysics::Galaxy Astrophysics, 010308 nuclear & particles physics, magnetic fields [ISM], Astronomy and Astrophysics, LOFAR, ISM [Radio continuum], Astrophysics - Astrophysics of Galaxies, Galaxy, Interstellar medium, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Astrophysics of Galaxies (astro-ph.GA), TELESCOPES, EMISSION, SKY SURVEY, ROTATION MEASURE SYNTHESIS
Abstract: The new generation of low-frequency radio telescopes, such as the Low Frequency Array (LOFAR: a Square Kilometre Array-low pathfinder), provides advancements in our capability of probing Galactic magnetism through low-frequency polarimetry. Maps of diffuse polarized radio emission and Faraday rotation can be used to infer properties of, and trace structure in, the magnetic fields in the ISM. However, to date very little of the sky has been probed at high angular and Faraday depth resolution. We observed a 5x5 degree region centred on the nearby galaxy IC342 using LOFAR in the frequency range 115-178 MHz at 4 arcmin resolution and performed Faraday tomography to detect foreground Galactic polarized synchrotron emission separated by Faraday depth (different amounts of Faraday rotation). Our Faraday depth cube shows rich polarized structure, with up to 30 K of polarized emission at 150 MHz. We detect two overlapping diffuse polarized features that are clearly separated in Faraday depth. Faraday-thick structures at such low frequencies would be too strongly depolarized to explain the observations and are therefore rejected. Only Faraday thin structures will not be strongly depolarized; producing such structures requires localized variations in the ratio of synchrotron emissivity to Faraday depth per unit distance, which can arise from several physical phenomena, such as a transition between regions of ionized and neutral gas. We conclude that the observed polarized emission is Faraday thin, and propose that the emission originates from two neutral clouds in the local ISM. We have modeled the Faraday rotation for this line of sight and estimated that the line of sight component of magnetic field of the local ISM for this direction varies between -0.86 and +0.12 uG. We propose that this may be a useful method for mapping magnetic fields within the local ISM., Comment: 17 pages, 12 figures, accepted for publication in A&A
Published: 2016
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20. Calibrating high-precision Faraday rotation measurements for LOFAR and the next generation of low-frequency radio telescopes (Corrigendum)

Author: C. Sotomayor-Beltran, C. Sobey, J. W. T. Hessels, G. de Bruyn, A. Noutsos, A. Alexov, J. Anderson, A. Asgekar, I. M. Avruch, R. Beck, M. E. Bell, M. R. Bell, M. J. Bentum, G. Bernardi, P. Best, L. Birzan, A. Bonafede, F. Breitling, J. Broderick, W. N. Brouw, M. Brüggen, B. Ciardi, F. de Gasperin, R.-J. Dettmar, A. van Duin, S. Duscha, J. Eislöffel, H. Falcke, R. A. Fallows, R. Fender, C. Ferrari, W. Frieswijk, M. A. Garrett, J. Grießmeier, T. Grit, A. W. Gunst, T. E. Hassall, G. Heald, M. Hoeft, A. Horneffer, M. Iacobelli, E. Juette, A. Karastergiou, E. Keane, J. Kohler, M. Kramer, V. I. Kondratiev, L. V. E. Koopmans, M. Kuniyoshi, G. Kuper, J. van Leeuwen, P. Maat, G. Macario, S. Markoff, J. P. McKean, D. D. Mulcahy, H. Munk, E. Orru, H. Paas, M. Pandey-Pommier, M. Pilia, R. Pizzo, A. G. Polatidis, W. Reich, H. Röttgering, M. Serylak, J. Sluman, B. W. Stappers, M. Tagger, Y. Tang, C. Tasse, S. ter Veen, R. Vermeulen, R. J. van Weeren, R. A. M. J. Wijers, S. J. Wijnholds, M. W. Wise, O. Wucknitz, S. Yatawatta, P. Zarka, Astronomisches Institut der Ruhr-Universität Bochum, Ruhr-Universität Bochum [Bochum], Max-Planck-Institut für Radioastronomie (MPIFR), Netherlands Institute for Radio Astronomy (ASTRON), School of Oceanography [Seattle], University of Washington [Seattle], SRON Netherlands Institute for Space Research (SRON), Université de Tours (UT), CSIRO Astronomy and Space Science, Commonwealth Scientific and Industrial Research Organisation [Canberra] (CSIRO), University of Southampton, Max-Planck-Institut für Astrophysik (MPA), Max-Planck-Gesellschaft, Laboratoire de Physique Nucléaire et de Hautes Énergies (LPNHE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), University of Edinburgh, Leiden Observatory [Leiden], Universiteit Leiden, Jacobs University [Bremen], Leibniz-Institut für Astrophysik Potsdam (AIP), Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Max Planck Institute for Astrophysics, Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), Thüringer Landessternwarte Tautenburg (TLS), Institute of Mathematical and Physical Sciences, Department of Quantitative Methods, Università degli studi di Genova = University of Genoa (UniGe), Unité Scientifique de la Station de Nançay (USN), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], Department of Pure Mathematics and Mathematical Statistics (DPMMS), Faculty of mathematics Centre for Mathematical Sciences [Cambridge] (CMS), University of Cambridge [UK] (CAM)-University of Cambridge [UK] (CAM), Oxford Astrophysics, University of Oxford, Centre for Astrophysics and Supercomputing (Centre for Astrophysics and Supercomputing), Swinburne University of Technology [Melbourne], Hessisches Landesmuseum Darmstadt, Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), University of Groningen, Groningen, Netherlands, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Department of Physics-Electronics, Rhodes University, Grahamstown, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), SKA South Africa, Ska South Africa, Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University-Smithsonian Institution, Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, ANR-09-JCJC-0001,OPALES(2009), European Project: 224897,EC:FP7:PEOPLE,FP7-PEOPLE-2007-2-2-ERG,WIDEMAP(2008), Université de Tours, Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Pierre et Marie Curie - Paris 6 (UPMC), Universiteit Leiden [Leiden], Universita degli studi di Genova, Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), University of Oxford [Oxford], Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Harvard University [Cambridge]-Smithsonian Institution, and Smithsonian Institution-Harvard University [Cambridge]
Subjects: 010504 meteorology & atmospheric sciences, Astronomy, Astrophysics, Low frequency, 01 natural sciences, Radio telescope, symbols.namesake, Optics, 0103 physical sciences, Faraday effect, 010303 astronomy & astrophysics, GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries), 0105 earth and related environmental sciences, Physics, polarization, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], business.industry, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, LOFAR, techniques: polarimetric, 13. Climate action, Space and Planetary Science, [SDU]Sciences of the Universe [physics], symbols, business, addenda, errata
Abstract: International audience; Faraday rotation measurements using the current and next generation of low-frequency radio telescopes will provide a powerful probe of astronomical magnetic fields. However, achieving the full potential of these measurements requires accurate removal of the time-variable ionospheric Faraday rotation contribution. We present ionFR, a code that calculates the amount of ionospheric Faraday rotation for a specific epoch, geographic location, and line-of-sight. ionFR uses a number of publicly available, GPS-derived total electron content maps and the most recent release of the International Geomagnetic Reference Field. We describe applications of this code for the calibration of radio polarimetric observations, and demonstrate the high accuracy of its modeled ionospheric Faraday rotations using LOFAR pulsar observations. These show that we can accurately determine some of the highest-precision pulsar rotation measures ever achieved. Precision rotation measures can be used to monitor rotation measure variations – either intrinsic or due to the changing line-of-sight through the interstellar medium. This calibration is particularly important for nearby sources, where the ionosphere can contribute a significant fraction of the observed rotation measure. We also discuss planned improvements to ionFR, as well as the importance of ionospheric Faraday rotation calibration for the emerging generation of low-frequency radio telescopes, such as the SKA and its pathfinders.
Published: 2015

21. LOFAR sparse image reconstruction

Author: H. Garsden, J. N. Girard, J. L. Starck, S. Corbel, C. Tasse, A. Woiselle, J. P. McKean, A. S. van Amesfoort, J. Anderson, I. M. Avruch, R. Beck, M. J. Bentum, P. Best, F. Breitling, J. Broderick, M. Brüggen, H. R. Butcher, B. Ciardi, F. de Gasperin, E. de Geus, M. de Vos, S. Duscha, J. Eislöffel, D. Engels, H. Falcke, R. A. Fallows, R. Fender, C. Ferrari, W. Frieswijk, M. A. Garrett, J. Grießmeier, A. W. Gunst, T. E. Hassall, G. Heald, M. Hoeft, J. Hörandel, A. van der Horst, E. Juette, A. Karastergiou, V. I. Kondratiev, M. Kramer, M. Kuniyoshi, G. Kuper, G. Mann, S. Markoff, R. McFadden, D. McKay-Bukowski, D. D. Mulcahy, H. Munk, M. J. Norden, E. Orru, H. Paas, M. Pandey-Pommier, V. N. Pandey, G. Pietka, R. Pizzo, A. G. Polatidis, A. Renting, H. Röttgering, A. Rowlinson, D. Schwarz, J. Sluman, O. Smirnov, B. W. Stappers, M. Steinmetz, A. Stewart, J. Swinbank, M. Tagger, Y. Tang, S. Thoudam, C. Toribio, R. Vermeulen, C. Vocks, R. J. van Weeren, S. J. Wijnholds, M. W. Wise, O. Wucknitz, S. Yatawatta, P. Zarka, A. Zensus, Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), SAGEM Défense Sécurité [Massy], Netherlands Institute for Radio Astronomy (ASTRON), Delft University of Technology (TU Delft), SRON Netherlands Institute for Space Research (SRON), University of Edinburgh, Leibniz-Institut für Astrophysik Potsdam (AIP), Universität Hamburg (UHH), University of Southampton, Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), University of Oulu, Center for Information Technology CIT, Université de Groningen, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), ANR-10-LABX-0023,UnivEarthS,Earth - Planets - Universe: observation, modeling, transfer(2010), ANR-11-IDEX-0005,USPC,Université Sorbonne Paris Cité(2011), ANR-09-JCJC-0001,OPALES(2009), European Project: 228261,EC:FP7:ERC,ERC-2008-AdG,SPARSEASTRO(2009), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), High Energy Astrophys. & Astropart. Phys (API, FNWI), Rhodes University, SKA South Africa, Ska South Africa, Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), ANR-10-LABX-0023,Labex UnivEarthS, ANR-11-IDEX-0005-02 ,USPC : Projet Université Sorbonne Paris Cité,Initiatives d’excellence - Laboratoire d’excellence INFLAMEX, and ANR-09-JCJC-0001,OPALES,nOn-thermal Processes in gALaxy cluStErs(2009)
Subjects: Sparse image, Phased array, Computer science, Aperture synthesis, Astronomy, EWI-26158, ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION, FOS: Physical sciences, IR-96629, techniques: image processing, 02 engineering and technology, 01 natural sciences, methods: numerical, Radio telescope, symbols.namesake, 0103 physical sciences, 0202 electrical engineering, electronic engineering, information engineering, Angular resolution, GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries), 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), METIS-312678, Sparse matrix, image processing [techniques], Astrophysics::Instrumentation and Methods for Astrophysics, numerical [methods], 020206 networking & telecommunications, Astronomy and Astrophysics, LOFAR, Inverse problem, interferometric [techniques], Interferometry, techniques: interferometric – methods: numerical – techniques: image processing, techniques: image, Compressed sensing, Fourier transform, Space and Planetary Science, [SDU]Sciences of the Universe [physics], techniques: interferometric, symbols, processing, Deconvolution, Astrophysics - Instrumentation and Methods for Astrophysics, Algorithm
Abstract: Context. The LOw Frequency ARray (LOFAR) radio telescope is a giant digital phased array interferometer with multiple antennas distributed in Europe. It provides discrete sets of Fourier components of the sky brightness. Recovering the original brightness distribution with aperture synthesis forms an inverse problem that can be solved by various deconvolution and minimization methods Aims. Recent papers have established a clear link between the discrete nature of radio interferometry measurement and the "compressed sensing" (CS) theory, which supports sparse reconstruction methods to form an image from the measured visibilities. Empowered by proximal theory, CS offers a sound framework for efficient global minimization and sparse data representation using fast algorithms. Combined with instrumental direction-dependent effects (DDE) in the scope of a real instrument, we developed and validated a new method based on this framework Methods. We implemented a sparse reconstruction method in the standard LOFAR imaging tool and compared the photometric and resolution performance of this new imager with that of CLEAN-based methods (CLEAN and MS-CLEAN) with simulated and real LOFAR data Results. We show that i) sparse reconstruction performs as well as CLEAN in recovering the flux of point sources; ii) performs much better on extended objects (the root mean square error is reduced by a factor of up to 10); and iii) provides a solution with an effective angular resolution 2-3 times better than the CLEAN images. Conclusions. Sparse recovery gives a correct photometry on high dynamic and wide-field images and improved realistic structures of extended sources (of simulated and real LOFAR datasets). This sparse reconstruction method is compatible with modern interferometric imagers that handle DDE corrections (A- and W-projections) required for current and future instruments such as LOFAR and SKA, Published in A&A, 19 pages, 9 figures
Published: 2015

22. Lunar occultation of the diffuse radio sky: LOFAR measurements between 35 and 80 MHz

Author: Vibor Jelić, Martin Bell, Gottfried Mann, Michael W. Wise, Gianni Bernardi, Wilfred Frieswijk, Jörg R. Hörandel, Garrelt Mellema, J. W. Broderick, J. Anderson, E. de Geus, George Heald, Y. Tang, K. M. B. Asad, M. J. Norden, Heino Falcke, Michiel A. Brentjens, Luitje Koopmans, V. I. Kondratiev, Arthur Corstanje, de Antonius Bruyn, A. Renting, Michel Tagger, Ben Stappers, Elizabeth Fernandez, F. de Gasperin, S. Kazemi, Emanuela Orrú, O. Martinez-Rubi, Rob Fender, A. Nelles, Oleg Smirnov, Stefan J. Wijnholds, P. Lambropoulos, A. R. Offringa, Annalisa Bonafede, Emma Chapman, Hannes Jensen, E. Juette, D. Engels, Sera Markoff, C. Toribio, Abhik Ghosh, F. B. Abdalla, Rebecca McFadden, Roberto Pizzo, Marco Iacobelli, Sarod Yatawatta, S. Daiboo, Satyendra Thoudam, W. Reich, D. McKay-Bukowski, Dominik J. Schwarz, D. D. Mulcahy, A. H. Patil, Frank Breitling, Jochen Eislöffel, B. Ciardi, Maaijke Mevius, Mark J. Bentum, C. Tasse, V. Veligatla, A. G. Polatidis, Matthias Steinmetz, S. Bus, Vishambhar Pandey, M. Kuniyoshi, Philippe Zarka, S. ter Veen, Adam Deller, Chiara Ferrari, A. W. Gunst, Ashish Asgekar, Matthias Hoeft, Philip Best, A. Shulevski, John D. Swinbank, H. Munk, Marcus Brüggen, Geraint Harker, Jean-Mathias Grießmeier, Tim Hassall, Christian Vocks, Saleem Zaroubi, Rajat M. Thomas, John McKean, Harvey Butcher, M. Pandey-Pommier, S. Duscha, Harish Vedantham, Richard Fallows, M. A. Garrett, H. J. A. Röttgering, Olaf Wucknitz, G. Kuper, Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], UMR Peuplement Végétaux et Bioagresseurs en Milieu Tropical (UMR PVBMT - INRA), Institut National de la Recherche Agronomique (INRA), Netherlands Institute for Radio Astronomy (ASTRON), University College of London [London] (UCL), Laboratoire de Mécanique des Contacts et des Structures [Villeurbanne] (LaMCoS), Institut National des Sciences Appliquées de Lyon (INSA Lyon), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Université de Lyon-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Mécanique multiphysique pour les matériaux et les procédés (MULTIMAP), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Université de Lyon-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Laboratoire de Physique Nucléaire et de Hautes Énergies (LPNHE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Howard Hugues Medical Institute, Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Departamento de Geologıa, Universidad de Santiago de Chile [Santiago] (USACH), Advanced Computing and Microelectronics Unit [Kolkata] (ACMU), Indian Statistical Institute [Kolkata], Department of Physics and Astronomy [UCL London], Stockholm University, Department of process and energy, Delft University of Technology (TU Delft), Department of Physics, University of Crete [Heraklion] (UOC), Institute of Electronic Structure and Laser, Foundation for Research and Technology - Hellas (FORTH), Stockholm Observatory Department of Astronomy, Department of Physics and Astronomy [Ghent], Ghent University [Belgium] (UGENT), Spatial Ecology and Epidemiology Group, University of Oxford [Oxford], Plant Ind, Hort Unit, Commonwealth Scientific and Industrial Research Organisation [Canberra] (CSIRO), Institute for Mathematics Applied to Geoscience, National Center for Atmospheric Research [Boulder] (NCAR), CSIRO Astronomy and Space Science, University of Edinburgh, Jacobs University [Bremen], Leibniz-Institut für Astrophysik Potsdam (AIP), University of Southampton, Radboud university [Nijmegen], Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), Metacohorts Consortium, Thüringer Landessternwarte Tautenburg (TLS), Département de Géologie, Université de Montréal [Montréal], Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Unité Scientifique de la Station de Nançay (USN), Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Ruhr-Universität Bochum [Bochum], Max-Planck-Institut für Radioastronomie (MPIFR), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), University of Oulu, Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], Centre de Recherche Astrophysique de Lyon (CRAL), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École normale supérieure - Lyon (ENS Lyon), Interactions Son Musique Mouvement, Sciences et Technologies de la Musique et du Son (STMS), Université Pierre et Marie Curie - Paris 6 (UPMC)-IRCAM-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-IRCAM-Centre National de la Recherche Scientifique (CNRS), Rhodes University, Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH / Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures (DSMZ), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Department of Astrophysics [Nijmegen], Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Radboud university [Nijmegen]-Radboud university [Nijmegen], Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, Observatoire de Paris - Site de Paris (OP), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS), European Project: 258942,EC:FP7:ERC,ERC-2010-StG_20091028,FIRSTLIGHT(2010), Howard Hughes Medical Institute (HHMI), Universiteit Gent = Ghent University (UGENT), University of Oxford, Radboud University [Nijmegen], Université de Montréal (UdeM), Universiteit Leiden, Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche et Coordination Acoustique/Musique (IRCAM)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche et Coordination Acoustique/Musique (IRCAM)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Rhodes University, Grahamstown, Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Radboud University [Nijmegen]-Radboud University [Nijmegen], Agence Nationale de la Recherche (ANR-09-JCJC-0001-01), Peuplements végétaux et bioagresseurs en milieu tropical (UMR PVBMT), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Université de La Réunion (UR), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Pierre et Marie Curie - Paris 6 (UPMC), Universiteit Gent = Ghent University [Belgium] (UGENT), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Vedantham, H.K., Koopmans, L.V.E., de Bruyn, A.G., Wijnholds, S.J., Brentjens, M., Abdalla, F.B., Asad, K.M.B., Bernardi, G., Bus, S., Chapman, E., Ciardi, B., Daiboo, S., Fernandez, E.R., Ghosh, A., Harker, G., Jelic, V., Jensen, H., Kazemi, S., Lambropoulos, P., Martinez-Rubi, O., Mellema, G., Mevius, M., Offringa, A.R., Pandey, V.N., Patil, A.H., Thomas, R.M., Veligatla, V., Yatawatta, S., Zaroubi, S., Anderson, J., Asgekar, A., Bell, M.E., Bentum, M.J., Best, P., Bonafede, A., Breitling, F., Broderick, J., Brüggen, M., Butcher, H.R., Corstanje, A., De Gasperin, F., De Geus, E., Deller, A., Duscha, S., Eislöffel, J., Engels, D., Falcke, H., Fallows, R.A., Fender, R., Ferrari, C., Frieswijk, W., Garrett, M.A., Grießmeier, J., Gunst, A.W., Hassall, T.E., Heald, G., Hoeft, M., Hörandel, J., Iacobelli, M., Juette, E., Kondratiev, V.I., Kuniyoshi, M., Kuper, G., Mann, G., Markoff, S., McFadden, R., McKay-Bukowski, D., McKean, J.P., Mulcahy, D.D., Munk, H., Nelles, A., Norden, M.J., Orru, E., Pandey-Pommier, M., Pizzo, R., Polatidis, A.G., Reich, W., Renting, A., Röttgering, H., Schwarz, D., Shulevski, A., Smirnov, O., Stappers, B.W., Steinmetz, M., Swinbank, J., Tagger, M., Tang, Y., Tasse, C., Ter Veen, S., Thoudam, S., Toribio, C., Vocks, C., Wise, M.W., Wucknitz, O., Zarka, P., Astronomy, Kapteyn Astronomical Institute, ITA, GBR, FRA, DEU, NLD, and High Energy Astrophys. & Astropart. Phys (API, FNWI)
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO), media_common.quotation_subject, Astrophysics::High Energy Astrophysical Phenomena, Astronomy, first stars, observational [methods], FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, methods: observational, techniques: interferometric, Moon, dark ages, reionization, methods: observational – techniques: interferometric – Moon – cosmology: dark ages, Occultation, IR-98655, Reionization, Instrumentation and Methods for Astrophysics (astro-ph.IM), media_common, EWI-26150, Astroparticle physics, Physics, Epoch (reference date), Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, LOFAR, Astronomy and Astrophysic, Universe, interferometric [techniques], Dark ages, reionization, first star, Sky, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Physics::Space Physics, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, Dark Ages, Astrophysics::Earth and Planetary Astrophysics, METIS-314921, Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: We present radio observations of the Moon between $35$ and $80$ MHz to demonstrate a novel technique of interferometrically measuring large-scale diffuse emission extending far beyond the primary beam (global signal) for the first time. In particular, we show that (i) the Moon appears as a negative-flux source at frequencies $35z>12$) and the Epoch of Reionization ($12>z>5$)., Comment: 15 pages, 11 figures, 1 table
Published: 2015

23. Resolved magnetic structures in the disk-halo interface of NGC 628

Author: D. D. Mulcahy, George Heald, Rainer Beck, and Astronomy
Subjects: H-ALPHA, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, STAR-FORMATION RATES, 01 natural sciences, law.invention, cosmic rays, law, Magnetic helicity, 0103 physical sciences, NEARBY GALAXIES, Pitch angle, HIGH-VELOCITY CLOUDS, Faraday cage, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, radio continuum: galaxies, Physics, INITIAL MASS FUNCTIONS, Spiral galaxy, IONIZED-GAS HALO, 010308 nuclear & particles physics, Astronomy and Astrophysics, RADIO-CONTINUUM SURVEY, Astrophysics - Astrophysics of Galaxies, Galaxy, FIELD UNIT OBSERVATIONS, Magnetic field, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Dynamo theory, FLUX-DENSITY SCALE, galaxies: magnetic fields, SPIRAL GALAXIES, galaxies: ISM, Dynamo
Abstract: Magnetic fields are essential to fully understand the interstellar medium (ISM) and its role in the disk-halo interface of galaxies is still poorly understood. Star formation is known to expel hot gas vertically into the halo and these outflows have important consequences for mean-field dynamo theory in that they can be efficient in removing magnetic helicity. We perform new observations of the nearby face-on spiral galaxy NGC 628 with the Karl G. Jansky Very Large Array (JVLA) at S-band and the Effelsberg 100-m telescope at frequencies of 2.6 GHz and 8.35 GHz. We obtain some of the most sensitive radio continuum images in both total and linearly polarised intensity of any external galaxy observed so far in addition to high-quality images of Faraday depth and polarisation angle from which we obtained evidence for drivers of magnetic turbulence in the disk-halo connection. Such drivers include a superbubble detected via a significant Faraday depth gradient coinciding with a HI hole. We observe an azimuthal periodic pattern in Faraday depth with a pattern wavelength of 3.7$\pm$ 0.1 kpc, indicating Parker instabilities. The lack of a significant anti-correlation between Faraday depth and magnetic pitch angle indicates that these loops are vertical in nature with little helical twisting, unlike in IC 342. We find that the magnetic pitch angle is systematically larger than the morphological pitch angle of the polarisation arms which gives evidence for the action of a large-scale dynamo where the regular magnetic field is not coupled to the gas flow and obtains a significant radial component. We additionally discover a lone region of ordered magnetic field to the north of the galaxy with a high degree of polarisation and a small pitch angle, a feature that has not been observed in any other galaxy so far and is possibly caused by an asymmetric HI hole., Comment: 25 pages, Accepted for publication in Astronomy and Astrophysics
Published: 2017

24. The nature of the low-frequency emission of M 51. First observations of a nearby galaxy with LOFAR

Author: D. D. Mulcahy, A. Horneffer, R. Beck, G. Heald, A. Fletcher, A. Scaife, B. Adebahr, J. M. Anderson, A. Bonafede, M. Brüggen, G. Brunetti, K. T. Chyży, J. Conway, R.-J. Dettmar, T. Enßlin, M. Haverkorn, C. Horellou, M. Iacobelli, F. P. Israel, H. Junklewitz, W. Jurusik, J. Köhler, M. Kuniyoshi, E. Orrú, R. Paladino, R. Pizzo, W. Reich, H. J. A. Röttgering, Astronomy, Mulcahy, D.D., Horneffer, A., Beck, R., Heald, G., Fletcher, A., Scaife, A., Adebahr, B., Anderson, J.M., Bonafede, A., Brüggen, M., Brunetti, G., Chyz Y, K.T., Conway, J., Dettmar, R.-J., Enßlin, T., Haverkorn, M., Horellou, C., Iacobelli, M., Israel, F.P., Junklewitz, H., Jurusik, W., Köhler, J., Kuniyoshi, M., Orrú, E., Paladino, R., Pizzo, R., Reich, W., and Röttgering, H.J.A.
Subjects: Astronomy, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Low frequency, Radio continuum: galaxie, Power law, magnetic fields [galaxies], cosmic rays, Galaxies: magnetic field, Absorption (electromagnetic radiation), GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries), Astrophysics::Galaxy Astrophysics, Physics, radio continuum: galaxies, polarization, Spiral galaxy, ISM [galaxies], Star formation, Astronomy and Astrophysics, LOFAR, Radius, Astronomy and Astrophysic, Cosmic ray, Astrophysics - Astrophysics of Galaxies, Galaxy, galaxies [radio continuum], Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), galaxies: magnetic fields, galaxies: ISM
Abstract: The grand-design spiral galaxy M51 was observed with the LOFAR High Frequency Antennas (HBA) and imaged in total intensity and polarisation. This observation covered the frequencies between 115 MHz and 175 MHz. We produced an image of total emission of M51 at the mean frequency of 151 MHz with 20 arcsec resolution and 0.3 mJy rms noise, which is the most sensitive image of a galaxy at frequencies below 300 MHz so far. The integrated spectrum of total radio emission is described well by a power law, while flat spectral indices in the central region indicate thermal absorption. We observe that the disk extends out to 16 kpc and see a break in the radial profile near the optical radius of the disk. Our main results, the scale lengths of the inner and outer disks at 151 MHz and 1.4 GHz, arm--interarm contrast, and the break scales of the radio--far-infrared correlations, can be explained consistently by CRE diffusion, leading to a longer propagation length of CRE of lower energy. The distribution of CRE sources drops sharply at about 10 kpc radius, where the star formation rate also decreases sharply. We find evidence that thermal absorption is primarily caused by HII regions. The non-detection of polarisation from M51 at 151 MHz is consistent with the estimates of Faraday depolarisation. Future searches for polarised emission in this frequency range should concentrate on regions with low star formation rates., 20 pages, 18 figures, accepted for publication in A&A
Published: 2014

25. Discovery of carbon radio recombination lines in absorption towards Cygnus A

Author: J. van Enst, D. Engels, J. B. R. Oonk, S. ter Veen, Tim Hassall, Leah K. Morabito, M. A. Garrett, Alexander G. G. M. Tielens, Ashish Asgekar, J. M. Anderson, Rainer Beck, D. D. Mulcahy, Neal Jackson, Frank Breitling, Vishambhar Pandey, Harvey Butcher, Rob Fender, James Miller-Jones, M. Pandey-Pommier, Sarod Yatawatta, Giulia Macario, Michel Tagger, J. Kohler, Anton Zensus, John Conway, H. J. A. Röttgering, Heino Falcke, H. Munk, Marcus Brüggen, A. Horneffer, Richard Fallows, Jochen Eislöffel, E. Juette, Olaf Wucknitz, P. Maat, M. J. Norden, A. Alexov, C. Vogt, Aris Karastergiou, Maaijke Mevius, G. Kuper, S. Duscha, V. I. Kondratiev, Michael W. Wise, Gianni Bernardi, Philip Best, Benjamin Stappers, Dominik J. Schwarz, Wilfred Frieswijk, Y. Tang, A. Shulevski, Anna M. M. Scaife, Chiara Ferrari, Glenn J. White, B. Ciardi, Marco Iacobelli, M. de Vos, Jean-Mathias Grießmeier, A. G. Polatidis, Arthur Corstanje, Matthias Hoeft, J. Sluman, John McKean, C. Tasse, John D. Swinbank, Francisco Salgado, J. W. Broderick, Roberto Pizzo, E. de Geus, Satyendra Thoudam, Ralph A. M. J. Wijers, Christian Vocks, Sera Markoff, C. Toribio, J. D. Mol, M. Kuniyoshi, Annalisa Bonafede, Jason W. T. Hessels, Michiel A. Brentjens, Mark J. Bentum, George Heald, Michael Kramer, J. van Leeuwen, Philippe Zarka, R. van Nieuwpoort, J. P. Hamaker, Charlotte Sobey, Emanuela Orrú, H. Paas, F. Batejat, W. Reich, Oleg Smirnov, F. de Gasperin, I. van Bemmel, Martin Bell, Gottfried Mann, Matthias Steinmetz, I. M. Avruch, R. J. van Weeren, Rene C. Vermeulen, Wouter Klijn, A. J. van der Horst, A. P. Schoenmakers, Netherlands Institute for Radio Astronomy (ASTRON), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University-Smithsonian Institution, Leiden Observatory [Leiden], Universiteit Leiden, Department of Physics and Astronomy [Milton Keynes], The Open University [Milton Keynes] (OU), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, SRON Netherlands Institute for Space Research (SRON), Max-Planck-Institut für Radioastronomie (MPIFR), Sydney Institute for Astronomy (SIfA), The University of Sydney, Department of Physics-Electronics, Rhodes University, Grahamstown, University of Edinburgh, Universität Hamburg (UHH), Leibniz-Institut für Astrophysik Potsdam (AIP), School of Physics and Astronomy [Southampton], University of Southampton, Onsala Space Observatory (OSO), Chalmers University of Technology [Göteborg], Radboud University [Nijmegen], Medstar Research Institute, Thüringer Landessternwarte Tautenburg (TLS), Hamburger Sternwarte/Hamburg Observatory, Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], University of Amsterdam [Amsterdam] (UvA), Ruhr-Universität Bochum [Bochum], Oxford Astrophysics, University of Oxford, Karlsruhe Institute of Technology (KIT), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Universität Bielefeld, Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, Observatoire de Paris - Site de Paris (OP), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Oonk, J.B.R., van Weeren, R.J., salgado, F., Morabito, L.K., Tielens, A.G.G.M., Rottgering, H.J.A., Asgekar, A., White, G.J., Alexov, A., Anderson, J., Avruch, I.M., Batejat, F., Beck, R., Be, M.E., van Bemmel, I., Bentum, M.J., Bernardi, G., Best, P., Bonafede, A., Breitling, F., Brentjens, M., Broderick, J., Brüggen, M., Butcher, H.R., Ciardi, B., Conway, J.E., Corstanje, A., de Gasperin, F., de Geus, E., de Vos, M., Duscha, S., Eislöffel, J., Engels, D., van Enst, J., Falcke, H., Fallows, R.A., Fender, R., Ferrari, C., Frieswijk, W., Garrett, M.A., Griemeier, J., Hamaker, J.P., Hassa, T.E., Heald, G., Hessels, J.W.T., Hoeft, M., Horneffer, A., van der Horst, A., Iacobelli, M., Jackson, N.J., Juette, E., Karastergiou, A., Klijn, W., Kohler, J., Kondratiev, V.I., Kramer, M., Kuniyoshi, M., Kuper, G., van Leeuwen, J., Maat, P., Macario, G., Mann, G., Markoff, S., McKean, J.P., Mevius, M., Miller-Jones, J.C.A., Mol, J.D., Mulcahy, D.D., Munk, H., Norden, M.J., Orru, E., Paas, H., Pandey-Pommier, M., Pandey, V.N., Pizzo, R., Polatidis, A.G., Reich, W., scaife, A.M.M., schoenmakers, A., schwarz, D., shulevski, A., sluman, J., smirnov, O., Sobey, C., Stappers, B.W., steinmetz, M., swinbank, J., Tagger, M., Tang, Y., Tasse, C., ter Veen, S., Thoudam, S., Toribio, C., van Nieuwpoort, R., Vermeulen, R., Vocks, C., Vogt, C., Wijers, R.A.M.J., Wise, M.W., Wucknitz, O., Yatawatta, S., Zarka, P., Zensus, A., Harvard University [Cambridge]-Smithsonian Institution, Universiteit Leiden [Leiden], Radboud university [Nijmegen], Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), University of Oxford [Oxford], École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Astronomy, and High Energy Astrophys. & Astropart. Phys (API, FNWI)
Subjects: [SDU.ASTR.CO]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], Astronomy, ISM: structure, Interstellar cloud, EWI-24499, FOS: Physical sciences, Astrophysics, structure-local interstellar matter-radio line, ISM [radio lines], Cygnus A, Absorption (electromagnetic radiation), Optical depth, Astrophysics::Galaxy Astrophysics, ISM, Line (formation), ISM: general, Physics, IsM, radio lines, radio lines: ISM, general [ISM], local interstellar matter, Local standard of rest, Astronomy and Astrophysics, METIS-302715, Astronomy and Astrophysic, Astrophysics - Astrophysics of Galaxies, Galaxy, Cassiopeia A, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, General-IsM, structure [ISM], IR-89519, ISM: general ISM: structure local interstellar matter radio lines: ISM
Abstract: We present the first detection of carbon radio recombination line absorption along the line of sight to Cygnus A. The observations were carried out with the LOw Frequency ARray in the 33 to 57 MHz range. These low frequency radio observations provide us with a new line of sight to study the diffuse, neutral gas in our Galaxy. To our knowledge this is the first time that foreground Milky Way recombination line absorption has been observed against a bright extragalactic background source. By stacking 48 carbon $\alpha$ lines in the observed frequency range we detect carbon absorption with a signal-to-noise ratio of about 5. The average carbon absorption has a peak optical depth of 2$\times$10$^{-4}$, a line width of 10 km s$^{-1}$ and a velocity of +4 km s$^{-1}$ with respect to the local standard of rest. The associated gas is found to have an electron temperature $T_{e}\sim$ 110 K and density $n_{e}\sim$ 0.06 cm$^{-3}$. These properties imply that the observed carbon $\alpha$ absorption likely arises in the cold neutral medium of the Orion arm of the Milky Way. Hydrogen and helium lines were not detected to a 3$\sigma$ peak optical depth limit of 1.5$\times$10$^{-4}$ for a 4 km s$^{-1}$ channel width. Radio recombination lines associated with Cygnus A itself were also searched for, but are not detected. We set a 3$\sigma$ upper limit of 1.5$\times$10$^{-4}$ for the peak optical depth of these lines for a 4 km s$^{-1}$ channel width., Comment: In press
Published: 2014

26. LOFAR tied-array imaging of Type III solar radio bursts

Author: Rene C. Vermeulen, John McKean, R. J. van Weeren, P. Maat, M. J. Norden, Gerard H. Kuper, Jean-Mathias Grießmeier, Sera Markoff, H. Paas, T. E. Hassall, V. I. Kondratiev, Jochen Eislöffel, Eoin P. Carley, A. G. Polatidis, A. A. Konovalenko, Hamish A. S. Reid, D. Engels, D. D. Mulcahy, Y. Tang, A. Nelles, Anna M. M. Scaife, A. Kerdraon, Oleg Smirnov, Olaf Wucknitz, Chiara Ferrari, Wolfgang Reich, Heino Falcke, Peter T. Gallagher, I. M. Avruch, Aris Karastergiou, Joel N. Bregman, H. Munk, Gianni Bernardi, Jörg R. Hörandel, Marcus Brüggen, Ashish Asgekar, F. de Gasperin, M. A. Garrett, W. Frieswijk, Marco Iacobelli, Pietro Zucca, E. de Geus, Sarod Yatawatta, Harvey Butcher, Diana E. Morosan, V. N. Pandey, Michel Tagger, Dominik J. Schwarz, Adam Stewart, M. Pandey-Pommier, E. Juette, Mark J. Bentum, Michael Kramer, A. W. Gunst, Emanuela Orru, S. Duscha, G. Pietka, H. O. Rucker, A. Horneffer, Philip Best, Matthias Hoeft, J. W. Broderick, C. Tasse, Gottfried Mann, R. Pizzo, James M. Anderson, M. Kuniyoshi, Ben Stappers, John Conway, Mario M. Bisi, Adam T. Deller, Christian Vocks, Alexander L. MacKinnon, Jasmina Magdalenic, Richard Fallows, Philippe Zarka, M. Serylak, Jason W. T. Hessels, Annalisa Bonafede, Benedetta Ciardi, C. Toribio, F. Breitling, Bo Thidé, H. J. A. Röttgering, Satyendra Thoudam, Morosan, D.E., Gallagher, P.T., Zucca, P., Fallows, R., Carley, E.P., Mann, G., Bisi, M.M., Kerdraon, A., Konovalenko, A.A., MacKinnon, A.L., Rucker, H.O., Thidé, B., Magdalenić, J., Vocks, C., Reid, H., Anderson, J., Asgekar, A., Avruch, I.M., Bentum, M.J., Bernardi, G., Best, P., Bonafede, A., Bregman, J., Breitling, F., Broderick, J., Brüggen, M., Butcher, H.R., Ciardi, B., Conway, J.E., De Gasperin, F., De Geus, E., Deller, A., Duscha, S., Eislöffel, J., Engels, D., Falcke, H., Ferrari, C., Frieswijk, W., Garrett, M.A., Grießmeier, J., Gunst, A.W., Hassall, T.E., Hessels, J.W.T., Hoeft, M., Hörandel, J., Horneffer, A., Iacobelli, M., Juette, E., Karastergiou, A., Kondratiev, V.I., Kramer, M., Kuniyoshi, M., Kuper, G., Maat, P., Markoff, S., McKean, J.P., Mulcahy, D.D., Munk, H., Nelles, A., Norden, M.J., Orru, E., Paas, H., Pandey-Pommier, M., Pandey, V.N., Pietka, G., Pizzo, R., Polatidis, A.G., Reich, W., Röttgering, H., Scaife, A.M.M., Schwarz, D., Serylak, M., Smirnov, O., Stappers, B.W., Stewart, A., Tagger, M., Tang, Y., Tasse, C., Thoudam, S., Toribio, C., Vermeulen, R., Van Weeren, R.J., Wucknitz, O., Yatawatta, S., Zarka, P., Trinity College Dublin, Leibniz-Institut für Astrophysik Potsdam (AIP), STFC Rutherford Appleton Laboratory (RAL), Science and Technology Facilities Council (STFC), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institute of Radio Astronomy of NASU [Kharkiv] (IRA), National Academy of Sciences of Ukraine (NASU), Lawrence Livermore National Laboratory (LLNL), Space Research Institute of Austrian Academy of Sciences (IWF), Austrian Academy of Sciences (OeAW), Swedish Institute of Space Physics [Uppsala] (IRF), SRON Netherlands Institute for Space Research (SRON), Jacobs University [Bremen], University of Southampton, Research School of Astronomy and Astrophysics [Canberra] (RSAA), Australian National University (ANU), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), Netherlands Institute for Radio Astronomy (ASTRON), Thüringer Landessternwarte Tautenburg (TLS), Radboud University [Nijmegen], Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Leiden Observatory [Leiden], Universiteit Leiden, Unité Scientifique de la Station de Nançay (USN), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Ruhr-Universität Bochum [Bochum], Max-Planck-Institut für Radioastronomie (MPIFR), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), National Radio Astronomy Observatory [Charlottesville] (NRAO), National Radio Astronomy Observatory (NRAO), School of Physics and Astronomy [Southampton], Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Université Paris-Sud - Paris 11 (UP11), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University-Smithsonian Institution, ANR-09-JCJC-0001,OPALES(2009), Kapteyn Astronomical Institute, Radboud university [Nijmegen], Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Universiteit Leiden [Leiden], Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Harvard University [Cambridge]-Smithsonian Institution, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Smithsonian Institution-Harvard University [Cambridge], ANR-09-JCJC-0001,OPALES,nOn-thermal Processes in gALaxy cluStErs(2009), and High Energy Astrophys. & Astropart. Phys (API, FNWI)
Subjects: 010504 meteorology & atmospheric sciences, corona [Sun], Astronomy, WAVES, Astrophysics, particle emission [Sun], 01 natural sciences, CORONA, EWI-25429, Sun: coronal, Coronal mass ejection, Astrophysics::Solar and Stellar Astrophysics, GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries), 010303 astronomy & astrophysics, Physics, Solar flare, Sun: radio radiation, [SDU.ASTR.HE]Sciences of the Universe [physics]/Astrophysics [astro-ph]/High Energy Astrophysical Phenomena [astro-ph.HE], ELECTRONS, Astrophysics - Solar and Stellar Astrophysics, Physical Sciences, IR-93233, Physics::Space Physics, SHOCK, Radio frequency, Astrophysics::Earth and Planetary Astrophysics, Sun: coronal mass ejections (CMEs), Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Solar radius, Astronomy & Astrophysics, ACCELERATION, Radio telescope, PLASMA EMISSION, SPACECRAFT, Sun: particle emission, 0103 physical sciences, Solar and Stellar Astrophysics (astro-ph.SR), 0105 earth and related environmental sciences, Science & Technology, RADIOHELIOGRAPH, radio radiation [Sun], [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Sun: corona, Astronomy and Astrophysics, LOFAR, METIS-309731, Astronomy and Astrophysic, Corona, coronal mass ejections (CMEs) [Sun], Space and Planetary Science, DENSITY, Temporal resolution, mass ejections (CMEs)
Abstract: The Sun is an active source of radio emission which is often associated with energetic phenomena such as solar flares and coronal mass ejections (CMEs). At low radio frequencies (, 9 pages, 6 figures
Published: 2014

27. Studying Galactic interstellar turbulence through fluctuations in synchrotron emission First LOFAR Galactic foreground detection

Author: Torsten A. Enßlin, I. van Bemmel, A. W. Gunst, H. Junklewitz, Wilfred Frieswijk, J. W. Broderick, Martin Bell, C. Vogt, Rainer Beck, M. Iacobelli, Cathy Horellou, E. de Geus, Vibor Jelić, Y. Tang, Sarod Yatawatta, Anna M. M. Scaife, Aris Karastergiou, R. J. van Weeren, Krzysztof T. Chyzy, J. Sluman, Michael W. Wise, Gianni Bernardi, Harvey Butcher, G. Mann, Jörg R. Hörandel, George Heald, J. van Leeuwen, D. D. Mulcahy, A. Horneffer, V. I. Kondratiev, M. Pandey-Pommier, Roberto Pizzo, Charlotte Sobey, Emanuela Orrú, Marcus Brüggen, W. Jurusik, Michel Tagger, C. Toribio, W. N. Brouw, R. Vermeulen, S. Duscha, F. de Gasperin, Jean-Mathias Griessmeier, I. M. Avruch, Heino Falcke, Gerard H. Kuper, John McKean, R. J. Dettmar, C. Tasse, Tim Hassall, Rosita Paladino, Ashish Asgekar, Anton Zensus, Michael R. Bell, Laura Birzan, J. P. Hamaker, H. J. A. Röttgering, Oleg Smirnov, Chiara Ferrari, Olaf Wucknitz, John Conway, W. Reich, Dominik J. Schwarz, Luitje Koopmans, P. Zarka, Matthias Hoeft, Carlos Sotomayor-Beltran, F. Breitling, D. Engels, H. Munk, Richard Fallows, A. Alexov, Philip Best, M. A. Garrett, C. Vocks, Jochen Eislöffel, Marijke Haverkorn, Annalisa Bonafede, B. Ciardi, M. Kuniyoshi, Matthias Steinmetz, Jason W. T. Hessels, Giulia Macario, Ben Stappers, A. G. Polatidis, Mark J. Bentum, Michael Kramer, James M. Anderson, Astronomy, Kapteyn Astronomical Institute, Iacobelli, M., Haverkorn, M., Orrú, E., Pizzo, R.F., Anderson, J., Beck, R., Bell, M.R., Bonafede, A., Chyzy, K., Dettmar, R.-J., Enßlin, T.A., Heald, G., Horellou, C., Horneffer, A., Jurusik, W., Junklewitz, H., Kuniyoshi, M., Mulcahy, D.D., Paladino, R., Reich, W., Scaife, A., Sobey, C., Sotomayor-Beltran, C., Alexov, A., Asgekar, A., Avruch, I.M., Bell, M.E., Van Bemmel, I., Bentum, M.J., Bernardi, G., Best, P., Birzan, L., Breitling, F., Broderick, J., Brouw, W.N., Brüggen, M., Butcher, H.R., Ciardi, B., Conway, J.E., De Gasperin, F., De Geus, E., Duscha, S., Eislöffel, J., Engels, D., Falcke, H., Fallows, R.A., Ferrari, C., Frieswijk, W., Garrett, M.A., Grießmeier, J., Gunst, A.W., Hamaker, J.P., Hassall, T.E., Hessels, J.W.T., Hoeft, M., Hörandel, J., Jelic, V., Karastergiou, A., Kondratiev, V.I., Koopmans, L.V.E., Kramer, M., Kuper, G., Van Leeuwen, J., MacArio, G., Mann, G., McKean, J.P., Munk, H., Pandey-Pommier, M., Polatidis, A.G., Röttgering, H., Schwarz, D., Sluman, J., Smirnov, O., Stappers, B.W., Steinmetz, M., Tagger, M., Tang, Y., Tasse, C., Toribio, C., Vermeulen, R., Vocks, C., Vogt, C., Van Weeren, R.J., Wise, M.W., Wucknitz, O., Yatawatta, S., Zarka, P., Zensus, A., and High Energy Astrophys. & Astropart. Phys (API, FNWI)
Subjects: ISM: general, ISM: magnetic fields, ISM: structure, radio continuum: general, radio continuum: ISM, techniques: interferometric, POLARIZATION, Astronomy, Continuum (design consultancy), Astrophysics, 01 natural sciences, Power law, GHZ, EWI-24132, 010303 astronomy & astrophysics, Physics, general [ISM], MAGNETIC-FIELD, Magnetic field, interferometric [techniques], METIS-302576, WIDE-FIELD, interferometric, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, Galactic coordinate system, general [radio continuum], ANGULAR POWER SPECTRUM, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Cosmic ray, ISM [radio continuum], IR-89497, Astrophysics::Cosmology and Extragalactic Astrophysics, ISM: magnetic field, radio continuum: ISM techniques, 0103 physical sciences, Radio continuum: ISM, ALGORITHM, Astrophysics::Galaxy Astrophysics, 010308 nuclear & particles physics, magnetic fields [ISM], Spectral density, Astronomy and Astrophysics, LOFAR, Astronomy and Astrophysic, Astrophysics - Astrophysics of Galaxies, W-PROJECTION, Galaxy, radiation mechanisms: non-thermal / galaxies: active / galaxies: individual: M 87 / galaxies: clusters: individual: Virgo / galaxies: jets / radio continuum: galaxies, GALAXY, 350 MHZ, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Techniques: interferometric, RADIO-EMISSION
Abstract: The characteristic outer scale of turbulence and the ratio of the random to ordered components of the magnetic field are key parameters to characterise magnetic turbulence in the interstellar gas, which affects the propagation of cosmic rays within the Galaxy. We provide new constraints to those two parameters. We use the LOw Frequency ARray (LOFAR) to image the diffuse continuum emission in the Fan region at (l,b) (137.0,+7.0) at 80"x70" resolution in the range [146,174] MHz. We detect multi-scale fluctuations in the Galactic synchrotron emission and compute their power spectrum. Applying theoretical estimates and derivations from the literature for the first time, we derive the outer scale of turbulence and the ratio of random to ordered magnetic field from the characteristics of these fluctuations . We obtain the deepest image of the Fan region to date and find diffuse continuum emission within the primary beam. The power spectrum of the foreground synchrotron fluctuations displays a power law behaviour for scales between 100 and 8 arcmin with a slope of (-1.84+/-0.19). We find an upper limit of about 20 pc for the outer scale of the magnetic interstellar turbulence toward the Fan region. We also find a variation of the ratio of random to ordered field as a function of Galactic coordinates, supporting different turbulent regimes. We use power spectra fluctuations from LOFAR as well as earlier GMRT and WSRT observations to constrain the outer scale of turbulence of the Galactic synchrotron foreground, finding a range of plausible values of 10-20 pc. Then, we use this information to deduce lower limits of the ratio of ordered to random magnetic field strength. These are found to be 0.3, 0.3, and 0.5 for the LOFAR, WSRT and GMRT fields considered respectively. Both these constraints are in agreement with previous estimates., Comment: 13 pages, 11 figures, accepted for publication in A&A
Published: 2013

28. Calibrating high-precision Faraday rotation measurements for LOFAR and the next generation of low-frequency radio telescopes

Author: Olaf Wucknitz, J. Kohler, D. D. Mulcahy, Aris Karastergiou, M. Iacobelli, Wilfred Frieswijk, Michael W. Wise, Gianni Bernardi, Philip Best, Gerard H. Kuper, V. I. Kondratiev, M. Pandey-Pommier, Y. Tang, Tim Hassall, Sarod Yatawatta, P. Maat, R. J. van Weeren, Evan Keane, George Heald, Frank Breitling, A. Noutsos, S. Duscha, H. Munk, R. C. Vermeulen, W. N. Brouw, J. Eisloeffel, John McKean, Stefan J. Wijnholds, T. Grit, Heino Falcke, J. Sluman, Roberto Pizzo, C. Tasse, Jean-Mathias Griessmeier, Rob Fender, I. M. Avruch, G. de Bruyn, Carlos Sotomayor-Beltran, Sera Markoff, M. Brueggen, Ralph A. M. J. Wijers, B. Ciardi, E. Juette, S. ter Veen, A. W. Gunst, Chiara Ferrari, M. Kuniyoshi, J. W. Broderick, Giulia Macario, Matthias Hoeft, A. Horneffer, M. Pilia, Michel Tagger, Jason W. T. Hessels, F. de Gasperin, Annalisa Bonafede, Richard Fallows, A. Alexov, Luitje Koopmans, Martin Bell, M. A. Garrett, Rainer Beck, M. Serylak, Michael Kramer, P. Zarka, Huub Roettgering, J. van Leeuwen, James M. Anderson, R. J. Dettmar, Mark J. Bentum, Ben Stappers, A. G. Polatidis, Laura Birzan, Ashish Asgekar, Charlotte Sobey, Emanuela Orrú, Michael R. Bell, A. van Duin, H. Paas, W. Reich, Astronomisches Institut der Ruhr-Universität Bochum, Ruhr-Universität Bochum [Bochum], Max-Planck-Institut für Radioastronomie (MPIFR), University of Amsterdam [Amsterdam] (UvA), Netherlands Institute for Radio Astronomy (ASTRON), SRON Netherlands Institute for Space Research (SRON), Laboratoire de Chimie Physique Moléculaire (LCPM), Ecole Polytechnique Fédérale de Lausanne (EPFL), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University [Cambridge]-Smithsonian Institution, University of Edinburgh, Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Jacobs University [Bremen], Leibniz-Institut für Astrophysik Potsdam (AIP), University of Southampton, Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), Thüringer Landessternwarte Tautenburg (TLS), Radboud university [Nijmegen], Institute of Mathematical and Physical Sciences, Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], Oxford Astrophysics, University of Oxford [Oxford], Centre for Astrophysics and Supercomputing, Swinburne University of Technology [Melbourne], Karlsruhe Institute of Technology (KIT), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), Center for Information Technology CIT, Université de Groningen, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, ANR-09-JCJC-0001,OPALES(2009), Astronomy, Kapteyn Astronomical Institute, High Energy Astrophys. & Astropart. Phys (API, FNWI), Harvard University-Smithsonian Institution, Universiteit Leiden, Radboud University [Nijmegen], Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), University of Oxford, École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Sotomayor-Beltran, C., Sobey, C., Hessels, J.W.T., De Bruyn, G., Noutsos, A., Alexov, A., Anderson, J., Asgekar, A., Avruch, I.M., Beck, R., Bell, M.E., Bell, M.R., Bentum, M.J., Bernardi, G., Best, P., Birzan, L., Bonafede, A., Breitling, F., Broderick, J., Brouw, W.N., Brüggen, M., Ciardi, B., De Gasperin, F., Dettmar, R.-J., Van Duin, A., Duscha, S., Eislöffel, J., Falcke, H., Fallows, R.A., Fender, R., Ferrari, C., Frieswijk, W., Garrett, M.A., Grießmeier, J., Grit, T., Gunst, A.W., Hassall, T.E., Heald, G., Hoeft, M., Horneffer, A., Iacobelli, M., Juette, E., Karastergiou, A., Keane, E., Kohler, J., Kramer, M., Kondratiev, V.I., Koopmans, L.V.E., Kuniyoshi, M., Kuper, G., Van Leeuwen, J., Maat, P., MacArio, G., Markoff, S., McKean, J.P., Mulcahy, D.D., Munk, H., Orru, E., Paas, H., Pandey-Pommier, M., Pilia, M., Pizzo, R., Polatidis, A.G., Reich, W., Röttgering, H., Serylak, M., Sluman, J., Stappers, B.W., Tagger, M., Tang, Y., Tasse, C., Ter Veen, S., Vermeulen, R., Van Weeren, R.J., Wijers, R.A.M.J., Wijnholds, S.J., Wise, M.W., Wucknitz, O., Yatawatta, S., and Zarka, P.
Subjects: 010504 meteorology & atmospheric sciences, Astronomy, VLA, Polarimetry, FOS: Physical sciences, IR-89498, Astrophysics::Cosmology and Extragalactic Astrophysics, Rotation, 01 natural sciences, law.invention, Radio telescope, PULSAR ROTATION, symbols.namesake, MHZ, Pulsar, DISPERSION, law, 0103 physical sciences, Faraday effect, DEPOLARIZATION, Faraday cage, Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Physics, EWI-24501, polarization, Astrophysics::Instrumentation and Methods for Astrophysics, METIS-302716, Astronomy and Astrophysics, GALACTIC MAGNETIC-FIELD, LOFAR, Astronomy and Astrophysic, GALAXY, techniques: polarimetric, 13. Climate action, Space and Planetary Science, [SDU]Sciences of the Universe [physics], ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, symbols, ARRAY, Ionosphere, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: International audience; Faraday rotation measurements using the current and next generation of low-frequency radio telescopes will provide a powerful probe of astronomical magnetic fields. However, achieving the full potential of these measurements requires accurate removal of the time-variable ionospheric Faraday rotation contribution. We present ionFR, a code that calculates the amount of ionospheric Faraday rotation for a specific epoch, geographic location, and line-of-sight. ionFR uses a number of publicly available, GPS-derived total electron content maps and the most recent release of the International Geomagnetic Reference Field. We describe applications of this code for the calibration of radio polarimetric observations, and demonstrate the high accuracy of its modeled ionospheric Faraday rotations using LOFAR pulsar observations. These show that we can accurately determine some of the highest-precision pulsar rotation measures ever achieved. Precision rotation measures can be used to monitor rotation measure variations - either intrinsic or due to the changing line-of-sight through the interstellar medium. This calibration is particularly important for nearby sources, where the ionosphere can contribute a significant fraction of the observed rotation measure. We also discuss planned improvements to ionFR, as well as the importance of ionospheric Faraday rotation calibration for the emerging generation of low-frequency radio telescopes, such as the SKA and its pathfinders.
Published: 2013

29. LOFAR: The LOw-Frequency ARray

Author: M. P. van Haarlem, M. W. Wise, A. W. Gunst, G. Heald, J. P. McKean, J. W. T. Hessels, A. G. de Bruyn, R. Nijboer, J. Swinbank, R. Fallows, M. Brentjens, A. Nelles, R. Beck, H. Falcke, R. Fender, J. Hörandel, L. V. E. Koopmans, G. Mann, G. Miley, H. Röttgering, B. W. Stappers, R. A. M. J. Wijers, S. Zaroubi, M. van den Akker, A. Alexov, J. Anderson, K. Anderson, A. van Ardenne, M. Arts, A. Asgekar, I. M. Avruch, F. Batejat, L. Bähren, M. E. Bell, M. R. Bell, I. van Bemmel, P. Bennema, M. J. Bentum, G. Bernardi, P. Best, L. Bîrzan, A. Bonafede, A.-J. Boonstra, R. Braun, J. Bregman, F. Breitling, R. H. van de Brink, J. Broderick, P. C. Broekema, W. N. Brouw, M. Brüggen, H. R. Butcher, W. van Cappellen, B. Ciardi, T. Coenen, J. Conway, A. Coolen, A. Corstanje, S. Damstra, O. Davies, A. T. Deller, R.-J. Dettmar, G. van Diepen, K. Dijkstra, P. Donker, A. Doorduin, J. Dromer, M. Drost, A. van Duin, J. Eislöffel, J. van Enst, C. Ferrari, W. Frieswijk, H. Gankema, M. A. Garrett, F. de Gasperin, M. Gerbers, E. de Geus, J.-M. Grießmeier, T. Grit, P. Gruppen, J. P. Hamaker, T. Hassall, M. Hoeft, H. A. Holties, A. Horneffer, A. van der Horst, A. van Houwelingen, A. Huijgen, M. Iacobelli, H. Intema, N. Jackson, V. Jelic, A. de Jong, E. Juette, D. Kant, A. Karastergiou, A. Koers, H. Kollen, V. I. Kondratiev, E. Kooistra, Y. Koopman, A. Koster, M. Kuniyoshi, M. Kramer, G. Kuper, P. Lambropoulos, C. Law, J. van Leeuwen, J. Lemaitre, M. Loose, P. Maat, G. Macario, S. Markoff, J. Masters, R. A. McFadden, D. McKay-Bukowski, H. Meijering, H. Meulman, M. Mevius, E. Middelberg, R. Millenaar, J. C. A. Miller-Jones, R. N. Mohan, J. D. Mol, J. Morawietz, R. Morganti, D. D. Mulcahy, E. Mulder, H. Munk, L. Nieuwenhuis, R. van Nieuwpoort, J. E. Noordam, M. Norden, A. Noutsos, A. R. Offringa, H. Olofsson, A. Omar, E. Orrú, R. Overeem, H. Paas, M. Pandey-Pommier, V. N. Pandey, R. Pizzo, A. Polatidis, D. Rafferty, S. Rawlings, W. Reich, J.-P. de Reijer, J. Reitsma, G. A. Renting, P. Riemers, E. Rol, J. W. Romein, J. Roosjen, M. Ruiter, A. Scaife, K. van der Schaaf, B. Scheers, P. Schellart, A. Schoenmakers, G. Schoonderbeek, M. Serylak, A. Shulevski, J. Sluman, O. Smirnov, C. Sobey, H. Spreeuw, M. Steinmetz, C. G. M. Sterks, H.-J. Stiepel, K. Stuurwold, M. Tagger, Y. Tang, C. Tasse, I. Thomas, S. Thoudam, M. C. Toribio, B. van der Tol, O. Usov, M. van Veelen, A.-J. van der Veen, S. ter Veen, J. P. W. Verbiest, R. Vermeulen, N. Vermaas, C. Vocks, C. Vogt, M. de Vos, E. van der Wal, R. van Weeren, H. Weggemans, P. Weltevrede, S. White, S. J. Wijnholds, T. Wilhelmsson, O. Wucknitz, S. Yatawatta, P. Zarka, A. Zensus, J. van Zwieten, Netherlands Institute for Radio Astronomy (ASTRON), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Institute of Mathematical and Physical Sciences, Radboud university [Nijmegen], Laboratoire de Chimie Physique Moléculaire (LCPM), Ecole Polytechnique Fédérale de Lausanne (EPFL), Max-Planck-Institut für Radioastronomie (MPIFR), University of Southampton, Leibniz-Institut für Astrophysik Potsdam (AIP), Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Medical Center Haaglanden, SRON Netherlands Institute for Space Research (SRON), University of Edinburgh, Jacobs University [Bremen], Technische Universität Dresden = Dresden University of Technology (TU Dresden), Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Department of Reproduction and Development, Erasmus University Rotterdam, London Institute for Mathematical Sciences, Netherlands Centre for Biodiversity, Leiden, The Netherlands, Thüringer Landessternwarte Tautenburg (TLS), Laboratoire Réactions et Génie des Procédés (LRGP), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Medstar Research Institute, Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Plant Research International, Business Unit Bioscience, Wageningen University and Research [Wageningen] (WUR), Dipartimento di Matematica 'Guido Castelnuovo' [Roma I] (Sapienza University of Rome), Università degli Studi di Roma 'La Sapienza' = Sapienza University [Rome], Centre de Mathématiques Laurent Schwartz (CMLS), Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X), Peuplements végétaux et bioagresseurs en milieu tropical (UMR PVBMT), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Université de La Réunion (UR), Ruhr-Universität Bochum [Bochum], Oxford Astrophysics, University of Oxford [Oxford], Amsterdam Center for Multiscale Modeling, Vrije Universiteit Amsterdam [Amsterdam] (VU), Vrije Universiteit Medical Centre (VUMC), Queen's Medical Centre, National Radio Astronomy Observatory (NRAO), University of Oulu, Department of Economics, Bryant University, Center for Agricultural Research in Suriname CELOS and Department of Biology, Anton de Kom Universiteit van Suriname - Anton de Kom University of Suriname [Paramaribo] (UVS), DLR Institute of Aerospace Medicine, Deutsches Zentrum für Luft- und Raumfahrt [Köln] (DLR), Onsala Space Observatory (OSO), Chalmers University of Technology [Göteborg], Geophysical Institute [Bergen] (GFI / BiU), University of Bergen (UiB), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Department of Astronomy and Astrophysics [PennState], Pennsylvania State University (Penn State), Penn State System-Penn State System, Academic Medical Center - Academisch Medisch Centrum [Amsterdam] (AMC), School of Physics and Astronomy [Southampton], Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Rhodes University, Grahamstown, Center for Information Technology CIT, Université de Groningen, Processus d'Activation Sélective par Transfert d'Energie Uni-électronique ou Radiatif (UMR 8640) (PASTEUR), Université Pierre et Marie Curie - Paris 6 (UPMC)-Département de Chimie - ENS Paris, École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Center for Operations and Econometrics, Center of Operation Research and Econometrics [Louvain] (CORE), Université Catholique de Louvain = Catholic University of Louvain (UCL)-Université Catholique de Louvain = Catholic University of Louvain (UCL), Finca El Encin, Instituto Madrileño de Investigación y Desarrollo Rural, Agrario y Alimentario (IMIDRA), Department of Surgery (EINDHOVEN - Surgery), Catharina Hospital, Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Harvard-Smithsonian Center for Astrophysics (CfA), Smithsonian Institution-Harvard University [Cambridge], Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, ANR-09-JCJC-0001,OPALES(2009), Astronomy, KVI - Center for Advanced Radiation Technology, Radboud University [Nijmegen], Universiteit Leiden, Università degli Studi di Roma 'La Sapienza' = Sapienza University [Rome] (UNIROMA), École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), University of Oxford, École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Harvard University-Smithsonian Institution, UMR Peuplement Végétaux et Bioagresseurs en Milieu Tropical (UMR PVBMT - INRA), Institut National de la Recherche Agronomique (INRA), Laboratoire de Physique Nucléaire et de Hautes Énergies (LPNHE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Technische Universität Dresden (TUD), university Rotterdam, PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Wageningen University and Research Centre [Wageningen] (WUR), Università degli Studi di Roma 'La Sapienza' [Rome], Department of Physics, University of Crete [Heraklion] (UOC), Institute of Electronic Structure and Laser, Foundation for Research and Technology - Hellas (FORTH), Anton de Kom University of Suriname, Geophysical Institute [Bergen], University of Bergen (UIB), Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Rhodes University, École normale supérieure - Paris (ENS Paris)-École normale supérieure - Paris (ENS Paris)-Centre National de la Recherche Scientifique (CNRS), SKA South Africa, Ska South Africa, Center for Operations and Econometrics, Universit´e catholique de Louvain and Fonds National de la Recherche Scientifique, Harvard University [Cambridge]-Smithsonian Institution, Observatoire de Paris - Site de Paris (OP), PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS), ANR-09-JCJC-0001,OPALES,nOn-thermal Processes in gALaxy cluStErs(2009), High Energy Astrophys. & Astropart. Phys (API, FNWI), Van Haarlem, M.P., Wise, M.W., Gunst, A.W., Heald, G., McKean, J.P., Hessels, J.W.T., De Bruyn, A.G., Nijboer, R., Swinbank, J., Fallows, R., Brentjens, M., Nelles, A., Beck, R., Falcke, H., Fender, R., Hörandel, J., Koopmans, L.V.E., Mann, G., Miley, G., Röttgering, H., Stappers, B.W., Wijers, R.A.M.J., Zaroubi, S., Van Den Akker, M., Alexov, A., Anderson, J., Anderson, K., Van Ardenne, A., Arts, M., Asgekar, A., Avruch, I.M., Batejat, F., Bähren, L., Bell, M.E., Bell, M.R., Van Bemmel, I., Bennema, P., Bentum, M.J., Bernardi, G., Best, P., Bîrzan, L., Bonafede, A., Boonstra, A.-J., Braun, R., Bregman, J., Breitling, F., Van De Brink, R.H., Broderick, J., Broekema, P.C., Brouw, W.N., Brüggen, M., Butcher, H.R., Van Cappellen, W., Ciardi, B., Coenen, T., Conway, J., Coolen, A., Corstanje, A., Damstra, S., Davies, O., Deller, A.T., Dettmar, R.-J., Van Diepen, G., Dijkstra, K., Donker, P., Doorduin, A., Dromer, J., Drost, M., Van Duin, A., Eislöffel, J., Van Enst, J., Ferrari, C., Frieswijk, W., Gankema, H., Garrett, M.A., De Gasperin, F., Gerbers, M., De Geus, E., Grießmeier, J.-M., Grit, T., Gruppen, P., Hamaker, J.P., Hassall, T., Hoeft, M., Holties, H.A., Horneffer, A., Van Der Horst, A., Van Houwelingen, A., Huijgen, A., Iacobelli, M., Intema, H., Jackson, N., Jelic, V., De Jong, A., Juette, E., Kant, D., Karastergiou, A., Koers, A., Kollen, H., Kondratiev, V.I., Kooistra, E., Koopman, Y., Koster, A., Kuniyoshi, M., Kramer, M., Kuper, G., Lambropoulos, P., Law, C., Van Leeuwen, J., Lemaitre, J., Loose, M., Maat, P., Macario, G., Markoff, S., Masters, J., McFadden, R.A., McKay-Bukowski, D., Meijering, H., Meulman, H., Mevius, M., Middelberg, E., Millenaar, R., Miller-Jones, J.C.A., Mohan, R.N., Mol, J.D., Morawietz, J., Morganti, R., Mulcahy, D.D., Mulder, E., Munk, H., Nieuwenhuis, L., Van Nieuwpoort, R., Noordam, J.E., Norden, M., Noutsos, A., Offringa, A.R., Olofsson, H., Omar, A., Orrú, E., Overeem, R., Paas, H., Pandey-Pommier, M., Pandey, V.N., Pizzo, R., Polatidis, A., Rafferty, D., Rawlings, S., Reich, W., De Reijer, J.-P., Reitsma, J., Renting, G.A., Riemers, P., Rol, E., Romein, J.W., Roosjen, J., Ruiter, M., Scaife, A., Van Der Schaaf, K., Scheers, B., Schellart, P., Schoenmakers, A., Schoonderbeek, G., Serylak, M., Shulevski, A., Sluman, J., Smirnov, O., Sobey, C., Spreeuw, H., Steinmetz, M., Sterks, C.G.M., Stiepel, H.-J., Stuurwold, K., Tagger, M., Tang, Y., Tasse, C., Thomas, I., Thoudam, S., Toribio, M.C., Van Der Tol, B., Usov, O., Van Veelen, M., Van Der Veen, A.-J., Ter Veen, S., Verbiest, J.P.W., Vermeulen, R., Vermaas, N., Vocks, C., Vogt, C., De Vos, M., Van Der Wal, E., Van Weeren, R., Weggemans, H., Weltevrede, P., White, S., Wijnholds, S.J., Wilhelmsson, T., Wucknitz, O., Yatawatta, S., Zarka, P., Zensus, A., and Van Zwieten, J.
Subjects: instrumentation: interferometers -radio continuum: general -radio lines: general -dark ages, Computer science, Astronomy, INTERPLANETARY SCINTILLATION, radio continuum: general, 7. Clean energy, 01 natural sciences, Precision Array for Probing the Epoch of Reionization, law.invention, Observatory, law, first stars - telescopes, dark ages, instrumentation: interferometers, 010303 astronomy & astrophysics, Telescope, UNDERSTANDING RADIO POLARIMETRY, Instrumentation: Interferometer, SELF-CALIBRATION, Interferometry, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, reionization, Astrophysics - Instrumentation and Methods for Astrophysics, radio lines: general, first stars, Z-GREATER-THAN-5.7 QUASARS, FOS: Physical sciences, Murchison Widefield Array, 0103 physical sciences, RAY AIR-SHOWERS, Angular resolution, dark ages, reionization, first stars, Instrumentation and Methods for Astrophysics (astro-ph.IM), Remote sensing, 010308 nuclear & particles physics, telescopes, Astronomy and Astrophysics, LOFAR, Astronomy and Astrophysic, Sextant (astronomical), Dark ages, reionization, first star, Space and Planetary Science, [SDU]Sciences of the Universe [physics], PROBE WMAP OBSERVATIONS, DIGITAL SKY SURVEY, HIGH-REDSHIFT, MONTE-CARLO SIMULATIONS, INTERGALACTIC MEDIUM
Abstract: LOFAR, the LOw-Frequency ARray, is a new-generation radio interferometer constructed in the north of the Netherlands and across europe. Utilizing a novel phased-array design, LOFAR covers the largely unexplored low-frequency range from 10-240 MHz and provides a number of unique observing capabilities. Spreading out from a core located near the village of Exloo in the northeast of the Netherlands, a total of 40 LOFAR stations are nearing completion. A further five stations have been deployed throughout Germany, and one station has been built in each of France, Sweden, and the UK. Digital beam-forming techniques make the LOFAR system agile and allow for rapid repointing of the telescope as well as the potential for multiple simultaneous observations. With its dense core array and long interferometric baselines, LOFAR achieves unparalleled sensitivity and angular resolution in the low-frequency radio regime. The LOFAR facilities are jointly operated by the International LOFAR Telescope (ILT) foundation, as an observatory open to the global astronomical community. LOFAR is one of the first radio observatories to feature automated processing pipelines to deliver fully calibrated science products to its user community. LOFAR's new capabilities, techniques and modus operandi make it an important pathfinder for the Square Kilometre Array (SKA). We give an overview of the LOFAR instrument, its major hardware and software components, and the core science objectives that have driven its design. In addition, we present a selection of new results from the commissioning phase of this new radio observatory., Comment: 56 pages, 34 figures, accepted for publication by A&A
Published: 2013
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30. LOFAR detections of low-frequency radio recombination lines towards Cassiopeia A

Author: Jochen Eislöffel, Maaijke Mevius, R. J. van Weeren, Ralph A. M. J. Wijers, A. G. Polatidis, D. McKay-Bukowski, Chiara Ferrari, John Conway, Wilfred Frieswijk, Y. Tang, Glenn J. White, Robert Braun, Michael R. Bell, J. Sluman, W. A. van Cappellen, V. N. Pandey, Richard Fallows, Raffaella Morganti, H. J. A. Röttgering, Philip Best, M. A. Garrett, T. Grit, Charlotte Sobey, Emanuela Orrú, I. M. Avruch, P. Maat, M. J. Norden, Rainer Beck, D. D. Mulcahy, Michel Tagger, Annalisa Bonafede, James Miller-Jones, Aris Karastergiou, Sarod Yatawatta, J.-M. Grießmeier, J. B. R. Oonk, H. Paas, B. Ciardi, C. Tasse, Michael W. Wise, Heino Falcke, Gianni Bernardi, Ashish Asgekar, M. Kuniyoshi, Oleg Smirnov, Matthias Steinmetz, J. Kohler, Marco Iacobelli, E. Juette, John McKean, H. Munk, Marcus Brüggen, Harvey Butcher, G. Kuper, J. M. Anderson, V. I. Kondratiev, Christian Vocks, T. E. Hassall, M. Pandey-Pommier, Casey J. Law, F. Breitling, M. de Vos, A. W. Gunst, S. Duscha, Neal Jackson, Olaf Wucknitz, Sera Markoff, A. de Jong, Laura Birzan, Giulia Macario, A. Schoenmakers, Wolfgang Reich, Huib Intema, J. W. Broderick, J. D. Mol, E. de Geus, Jason W. T. Hessels, R. Pizzo, P. Zarka, George Heald, Mark J. Bentum, W. N. Brouw, Gottfried Mann, R. Vermeulen, Matthias Hoeft, F. Batejat, Bart Scheers, I. van Bemmel, Martin Bell, F. de Gasperin, J. van Leeuwen, R. H. van de Brink, Netherlands Institute for Radio Astronomy (ASTRON), Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Harvard-Smithsonian Center for Astrophysics (CfA), Smithsonian Institution-Harvard University [Cambridge], SLAC National Accelerator Laboratory (SLAC), Stanford University, Jodrell Bank Cent. for Astrophysics, University of Manchester [Manchester], Max-Planck-Institut für Radioastronomie (MPIFR), SRON Netherlands Institute for Space Research (SRON), Onsala Space Observatory (OSO), Chalmers University of Technology [Göteborg], Laboratoire de Chimie Physique Moléculaire (LCPM), Ecole Polytechnique Fédérale de Lausanne (EPFL), University of Southampton, Laboratoire de Physique Nucléaire et de Hautes Énergies (LPNHE), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Pierre et Marie Curie - Paris 6 (UPMC), University of Edinburgh, Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Jacobs University [Bremen], Technische Universität Dresden = Dresden University of Technology (TU Dresden), Leibniz-Institut für Astrophysik Potsdam (AIP), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), Medstar Research Institute, Thüringer Landessternwarte Tautenburg (TLS), Radboud university [Nijmegen], Institute of Mathematical and Physical Sciences, Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO), Jodrell Bank Centre for Astrophysics, University of Amsterdam [Amsterdam] (UvA), Dipartimento di Matematica 'Guido Castelnuovo' [Roma I] (Sapienza University of Rome), Università degli Studi di Roma 'La Sapienza' = Sapienza University [Rome], Centre de Mathématiques Laurent Schwartz (CMLS), Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X), Ruhr-Universität Bochum [Bochum], Oxford Astrophysics, University of Oxford [Oxford], Karlsruhe Institute of Technology (KIT), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Oulu, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), National Radio Astronomy Observatory [Charlottesville] (NRAO), National Radio Astronomy Observatory (NRAO), Rhodes University, Grahamstown, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, ANR-09-JCJC-0001,OPALES(2009), Harvard University-Smithsonian Institution, Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Universiteit Leiden, Radboud University [Nijmegen], Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Università degli Studi di Roma 'La Sapienza' = Sapienza University [Rome] (UNIROMA), École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), University of Oxford, École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Asgekar, A., Oonk, J.B.R., Yatawatta, S., Van Weeren, R.J., McKean, J.P., White, G., Jackson, N., Anderson, J., Avruch, I.M., Batejat, F., Beck, R., Bell, M.E., Bell, M.R., Van Bemmel, I., Bentum, M.J., Bernardi, G., Best, P., Bîrzan, L., Bonafede, A., Braun, R., Breitling, F., Van De Brink, R.H., Broderick, J., Brouw, W.N., Brüggen, M., Butcher, H.R., Van Cappellen, W., Ciardi, B., Conway, J.E., De Gasperin, F., De Geus, E., De Jong, A., De Vos, M., Duscha, S., Eislöffel, J., Falcke, H., Fallows, R.A., Ferrari, C., Frieswijk, W., Garrett, M.A., Grießmeier, J.-M., Grit, T., Gunst, A.W., Hassall, T.E., Heald, G., Hessels, J.W.T., Hoeft, M., Iacobelli, M., Intema, H., Juette, E., Karastergiou, A., Kohler, J., Kondratiev, V.I., Kuniyoshi, M., Kuper, G., Law, C., Van Leeuwen, J., Maat, P., MacArio, G., Mann, G., Markoff, S., McKay-Bukowski, D., Mevius, M., Miller-Jones, J.C.A., Mol, J.D., Morganti, R., Mulcahy, D.D., Munk, H., Norden, M.J., Orru, E., Paas, H., Pandey-Pommier, M., Pandey, V.N., Pizzo, R., Polatidis, A.G., Reich, W., Röttgering, H., Scheers, B., Schoenmakers, A., Sluman, J., Smirnov, O., Sobey, C., Steinmetz, M., Tagger, M., Tang, Y., Tasse, C., Vermeulen, R., Vocks, C., Wijers, R.A.M.J., Wise, M.W., Wucknitz, O., Zarka, P., High Energy Astrophys. & Astropart. Phys (API, FNWI), Astronomy, and Kapteyn Astronomical Institute
Subjects: Astronomy, chemistry.chemical_element, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, ISM: individual objects: Cassiopeia A, IR-89496, Astronomy & Astrophysics, Low frequency, ISM: individual objects: Cas siopeia A, 01 natural sciences, ISM: clouds, Spectral line, CARBON, MHZ, ISM: cloud, 0103 physical sciences, EWI-24495, Spectral resolution, Supernova remnant, 010303 astronomy & astrophysics, Helium, Radio lines: ISM, Astrophysics::Galaxy Astrophysics, Line (formation), Physics, radio lines : ISM, 010308 nuclear & particles physics, Astronomy and Astrophysics, LOFAR, Astronomy and Astrophysic, REGIONS, Astrophysics - Astrophysics of Galaxies, METIS-302711, Cassiopeia A, chemistry, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, ISM: clouds / radio lines: ISM / ISM: individual objects: Cassiopeia A, [SDU.ASTR.GA]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA]
Abstract: Cassiopeia A was observed using the Low-Band Antennas of the LOw Frequency ARray (LOFAR) with high spectral resolution. This allowed a search for radio recombination lines (RRLs) along the line-of-sight to this source. Five carbon-alpha RRLs were detected in absorption between 40 and 50 MHz with a signal-to-noise ratio of > 5 from two independent LOFAR datasets. The derived line velocities (v_LSR ~ -50 km/s) and integrated optical depths (~ 13 s^-1) of the RRLs in our spectra, extracted over the whole supernova remnant, are consistent within each LOFAR dataset and with those previously reported. For the first time, we are able to extract spectra against the brightest hotspot of the remnant at frequencies below 330 MHz. These spectra show significantly higher (15-80 %) integrated optical depths, indicating that there is small-scale angular structure on the order of ~1 pc in the absorbing gas distribution over the face of the remnant. We also place an upper limit of 3 x 10^-4 on the peak optical depths of hydrogen and helium RRLs. These results demonstrate that LOFAR has the desired spectral stability and sensitivity to study faint recombination lines in the decameter band., Accepted for publication in A&A Letters; 5 pages, 4 colour figures
Published: 2013

31. Detecting cosmic rays with the LOFAR radio telescope

Author: P. Maat, M. J. Norden, J. M. Anderson, N. J. Vermaas, E. de Geus, Sarod Yatawatta, Stefan J. Wijnholds, A. de Jong, J. D. Mol, Ben Stappers, C. Vogt, Philip Best, Pim Schellart, Stijn Buitink, D. McKay-Bukowski, M. Pandey-Pommier, Joel N. Bregman, H. Munk, Marcus Brüggen, Matthias Hoeft, P. Bennema, Jason W. T. Hessels, Charlotte Sobey, Benedetta Ciardi, M. de Vos, R.V. van Nieuwpoort, J. E. Enriquez, A. Alexov, R. J. van Weeren, S. Duscha, L. Bähren, Ph. Zarka, Aris Karastergiou, Gottfried Mann, Heino Falcke, Rene C. Vermeulen, V. I. Kondratiev, A. Horneffer, Michael W. Wise, Gianni Bernardi, R. Pizzo, D. D. Mulcahy, M. Kuniyoshi, Giulia Macario, Jörg R. Hörandel, Michael Kramer, Ralph A. M. J. Wijers, Richard Fallows, John McKean, Arthur Corstanje, Cyril Tasse, J. W. Broderick, A. H. W. M. Coolen, A. Nelles, George Heald, A. Zensus, A. Schoenmakers, John W. Romein, Michiel A. Brentjens, John D. Swinbank, C. Toribio, Jean-Mathias Grießmeier, Maria Krause, M. A. Garrett, Olaf Scholten, Dominik J. Schwarz, Y. Tang, M. van den Akker, T. E. Hassall, Oleg Smirnov, H. Paas, T. Grit, James Miller-Jones, R. Nijboer, Matthias Steinmetz, Marco Iacobelli, J. P. Hamaker, Emanuela Orru, C. W. James, J. van Leeuwen, J. Kohler, Chiara Ferrari, Christian Vocks, Jochen Eislöffel, Mark J. Bentum, Gerard H. Kuper, R. Overeem, A. G. Polatidis, I. M. Avruch, A. Renting, F. de Gasperin, W. Frieswijk, S. ter Veen, Martin Bell, E. Juette, Wouter Klijn, M. Mevius, Sera Markoff, H. A. Holties, Olaf Wucknitz, Rainer Beck, J. Sluman, H. J. A. Röttgering, Satyendra Thoudam, F. Breitling, High Energy Astrophys. & Astropart. Phys (API, FNWI), Radboud University [Nijmegen], SETI Institute, Netherlands Institute for Radio Astronomy (ASTRON), Max-Planck-Institut für Radioastronomie (MPIFR), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Erlangen Centre for Astroparticle Physics (ECAP), Friedrich-Alexander Universität Erlangen-Nürnberg (FAU), Max-Planck-Institut für Extraterrestrische Physik (MPE), Kernfysisch Versneller Instituut, Univ. of Groningen (KVI), University of Groningen [Groningen], Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), SRON Netherlands Institute for Space Research (SRON), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Laboratoire de Chimie Physique Moléculaire (LCPM), Ecole Polytechnique Fédérale de Lausanne (EPFL), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University-Smithsonian Institution, University of Edinburgh, Leibniz-Institut für Astrophysik Potsdam (AIP), University of Southampton, Jacobs University [Bremen], London Institute for Mathematical Sciences, Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), Medstar Research Institute, Thüringer Landessternwarte Tautenburg (TLS), Institute of Mathematical and Physical Sciences, Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Leiden Observatory [Leiden], Universiteit Leiden, Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], Ruhr-Universität Bochum [Bochum], Oxford Astrophysics, University of Oxford, Karlsruhe Institute of Technology (KIT), University of Oulu, Center for Agricultural Research in Suriname CELOS and Department of Biology, Anton de Kom Universiteit van Suriname - Anton de Kom University of Suriname [Paramaribo] (UVS), Center for Information Technology CIT, Université de Groningen, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Interactions Son Musique Mouvement, Sciences et Technologies de la Musique et du Son (STMS), Institut de Recherche et Coordination Acoustique/Musique (IRCAM)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche et Coordination Acoustique/Musique (IRCAM)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Rhodes University, Grahamstown, SKA South Africa, Ska South Africa, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, Kapteyn Astronomical Institute [Groningen], ANR-09-JCJC-0001,OPALES(2009), European Project: 227610,EC:FP7:ERC,ERC-2008-AdG,LOFAR-AUGER(2009), Astronomy, Research unit Astroparticle Physics, Radboud university [Nijmegen], Harvard University [Cambridge]-Smithsonian Institution, Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Universiteit Leiden [Leiden], University of Oxford [Oxford], École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Anton de Kom University of Suriname, Université Pierre et Marie Curie - Paris 6 (UPMC)-IRCAM-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-IRCAM-Centre National de la Recherche Scientifique (CNRS), Rhodes University, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), and ANR-09-JCJC-0001,OPALES,nOn-thermal Processes in gALaxy cluStErs(2009)
Subjects: EWI-24497, Astronomy, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Cosmic ray, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Low frequency, EXTENSIVE AIR-SHOWERS, 01 natural sciences, Electromagnetic interference, Radio telescope, CODALEMA, 0103 physical sciences, instrumentation: interferometers, 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Physics, High Energy Astrophysical Phenomena (astro-ph.HE), 010308 nuclear & particles physics, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, LOFAR, METIS-302713, methods: data analysis, SIMULATIONS, PULSES, Interferometry, Space and Planetary Science, astroparticle physics, [SDU]Sciences of the Universe [physics], ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, ARRAY, astroparticle physics – methods: data analysis – instrumentation: interferometers, Antenna (radio), EMISSION, Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, Energy (signal processing), IR-89518
Abstract: International audience; The low frequency array (LOFAR), is the first radio telescope designed with the capability to measure radio emission from cosmic-ray induced air showers in parallel with interferometric observations. In the first $\sim 2\,\mathrm{years}$ of observing, 405 cosmic-ray events in the energy range of $10^{16} - 10^{18}\,\mathrm{eV}$ have been detected in the band from $30 - 80\,\mathrm{MHz}$. Each of these air showers is registered with up to $\sim1000$ independent antennas resulting in measurements of the radio emission with unprecedented detail. This article describes the dataset, as well as the analysis pipeline, and serves as a reference for future papers based on these data. All steps necessary to achieve a full reconstruction of the electric field at every antenna position are explained, including removal of radio frequency interference, correcting for the antenna response and identification of the pulsed signal.
Published: 2013

32. Corrigendum: A large light-mass component of cosmic rays at 1017–1017.5 electronvolts from radio observations

Author: Wilfred Frieswijk, M. P. van Haarlem, Anna M. M. Scaife, Vishambhar Pandey, M. C. Toribio, A. Horneffer, Michael Kramer, Jochen Eislöffel, S. ter Veen, Harvey Butcher, A. W. Gunst, J. van Leeuwen, Maaijke Mevius, G. van Diepen, E. de Geus, Sarod Yatawatta, Adam Stewart, Adam Deller, V. I. Kondratiev, M. Pandey-Pommier, Laura Rossetto, D. Carbone, A. Nelles, A. G. Polatidis, Tim Hassall, D. D. Mulcahy, James M. Anderson, S. Duscha, Ralph A. M. J. Wijers, J. Sluman, Roberto Pizzo, Marcus Brüggen, Rebecca McFadden, Hubertus Intema, E. Juette, Stijn Buitink, Satyendra Thoudam, Rob Fender, M. Serylak, R. C. Vermeulen, F. de Gasperin, Y. Tang, O. Scholten, Christian Vocks, J. W. Broderick, M. A. Garrett, P. Maat, M. J. Norden, John D. Swinbank, Heino Falcke, John McKean, H. J. A. Röttgering, Aris Karastergiou, Mark J. Bentum, M. Iacobelli, Arthur Corstanje, Sera Markoff, Benjamin Stappers, M. Tagger, Michael W. Wise, Gianni Bernardi, Jörg R. Hörandel, G. M. Loose, Dominik J. Schwarz, Martin Bell, C. Tasse, Frank Breitling, John Conway, Annalisa Bonafede, H. Paas, M. Steinmetz, Gottfried Mann, R. J. Dettmar, Stefan J. Wijnholds, George Heald, Jason W. T. Hessels, T. Huege, Oleg Smirnov, W. N. Brouw, P. Zarka, J.-M. Grießmeier, B. Ciardi, D. Engels, O. Wucknitz, J. E. Enriquez, M. Kuniyoshi, Richard Fallows, G. Kuper, W. Reich, M. Pietka, Emanuela Orrú, Ashish Asgekar, C. Vogt, Philip Best, Pim Schellart, J. P. Rachen, H. Munk, R. J. van Weeren, D. McKay-Bukowski, Chiara Ferrari, T. N. G. Trinh, Matthias Hoeft, J. A. Zensus, I. M. Avruch, Department of Astrophysics [Nijmegen], Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Radboud university [Nijmegen]-Radboud university [Nijmegen], Radboud university [Nijmegen], Karlsruher Institut für Technologie (KIT), Institute for Mathematics Applied to Geoscience, National Center for Atmospheric Research [Boulder] (NCAR), Netherlands Institute for Radio Astronomy (ASTRON), SRON Netherlands Institute for Space Research (SRON), CSIRO Astronomy and Space Science, Commonwealth Scientific and Industrial Research Organisation [Canberra] (CSIRO), University of Edinburgh, Jacobs University [Bremen], Leibniz-Institut für Astrophysik Potsdam (AIP), University of Southampton, Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], University of Amsterdam [Amsterdam] (UvA), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Medstar Research Institute, Astronomisches Institut der Ruhr-Universität Bochum, Ruhr-Universität Bochum [Bochum], Thüringer Landessternwarte Tautenburg (TLS), Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), Institut de Génomique Fonctionnelle de Lyon (IGFL), École normale supérieure - Lyon (ENS Lyon)-Institut National de la Recherche Agronomique (INRA)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), Département de Géologie, Université de Montréal [Montréal], Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], Rhodes University, Max-Planck-Institut für Radioastronomie (MPIFR), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Oulu, Center for Information Technology CIT, Université de Groningen, Centre de Recherche Astrophysique de Lyon (CRAL), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École normale supérieure - Lyon (ENS Lyon), Department of Physics and Astronomy [Ghent], Ghent University [Belgium] (UGENT), Oxford Astrophysics, University of Oxford [Oxford], School of Physics and Astronomy [Southampton], Interactions Son Musique Mouvement, Sciences et Technologies de la Musique et du Son (STMS), Université Pierre et Marie Curie - Paris 6 (UPMC)-IRCAM-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-IRCAM-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH / Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures (DSMZ), Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Université Libre de Bruxelles [Bruxelles] (ULB), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, Observatoire de Paris - Site de Paris (OP), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS), Radboud University [Nijmegen]-Radboud University [Nijmegen], Radboud University [Nijmegen], École normale supérieure de Lyon (ENS de Lyon)-Institut National de la Recherche Agronomique (INRA)-Université Claude Bernard Lyon 1 (UCBL), Université de Montréal (UdeM), Universiteit Leiden, Rhodes University, Grahamstown, École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Universiteit Gent = Ghent University (UGENT), University of Oxford, Institut de Recherche et Coordination Acoustique/Musique (IRCAM)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche et Coordination Acoustique/Musique (IRCAM)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Université libre de Bruxelles (ULB), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut National de la Recherche Agronomique (INRA)-École normale supérieure - Lyon (ENS Lyon), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Universiteit Gent = Ghent University [Belgium] (UGENT), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National d’Études Spatiales [Paris] (CNES)
Subjects: Pierre Auger Observatory, Astroparticle physics, Physics, [PHYS]Physics [physics], Multidisciplinary, 010504 meteorology & atmospheric sciences, High-energy astronomy, Astronomy, Electronvolt, Cosmic ray, LOFAR, Astrophysics, 01 natural sciences, Auger, International Cosmic Ray Conference, 0103 physical sciences, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences
Abstract: In this Letter, we omitted to cite preliminary results from the low-energy extension of the Pierre Auger Observatory, as presented at the International Cosmic Ray Conference 2015 (ref. 1). Figure 1 of this Corrigendum shows measurements of the average value of Xmax for the Low Frequency Array (LOFAR), and earlier experiments using different techniques, now including the data from the Pierre Auger Observatory1 , specifically the contribution of A. Porcelli. Our values are in agreement with those of ref. 1 within systematic uncertainties.
Published: 2016

33. Discovery of Carbon Radio Recombination Lines in M82

Author: D. D. Mulcahy, Matt J. Jarvis, Leah K. Morabito, Ivan Marti-Vidal, Marco Iacobelli, Gianfranco Brunetti, M. Carmen Toribio, Francisco Salgado, Rainer Beck, Emanuela Orru, J. B. R. Oonk, Roberto Pizzo, H. J. A. Röttgering, George Heald, B. Adebahr, Philip Best, Michael W. Wise, Krzysztof T. Chyzy, Alexander G. G. M. Tielens, J. Gregson, John Conway, Anna M. M. Scaife, Glenn J. White, Wim van Driel, Cathy Horellou, Robert Beswick, Reinout J. van Weeren, George K. Miley, Marcus Brüggen, A. Horneffer, Marijke Haverkorn, Annalisa Bonafede, Eskil Varenius, Morabito, Leah K., Oonk, J.B.R., Salgado, Francisco, Toribio, M. Carmen, Röttgering, H.J.A., Tielens, A.G.G.M., Beck, Rainer, Adebahr, Björn, Best, Philip, Beswick, Robert, Bonafede, Annalisa, Brunetti, Gianfranco, Brüggen, Marcu, Chyzy, Krzysztof T., Conway, J.E., Van Driel, Wim, Gregson, Jonathan, Haverkorn, Marijke, Heald, George, Horellou, Cathy, Horneffer, Andrea, Iacobelli, Marco, Jarvis, Matt J., Marti-Vidal, Ivan, Miley, George, Mulcahy, D.D., Orrú, Emanuela, Pizzo, Roberto, Scaife, A.M.M., Varenius, Eskil, Van Weeren, Reinout J., White, Glenn J., Wise, Michael W., Leiden Observatory [Leiden], Universiteit Leiden [Leiden], MRI Whale Unit, South African Museum, Onsala Space Observatory, Dept. of Radio and Space Science, Chalmers University of Technology, Chalmers University of Technology [Göteborg], Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Radboud university [Nijmegen], Onsala Space Observatory (OSO), Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], School of Physics and Astronomy [Southampton], University of Southampton, SLAC National Accelerator Laboratory (SLAC), Stanford University, Department of Astrophysical Sciences [Princeton], Princeton University, Kapteyn Astronomical Institute, and Astronomy
Subjects: Astronomy, FOS: Physical sciences, Starburst region, Astrophysics, Spectral line, galaxies: individual: M82, ISM [radio lines], galaxies: individual (M82), Optical depth (astrophysics), Absorption (electromagnetic radiation), ComputingMilieux_MISCELLANEOUS, Line (formation), ISM: general, radio lines: galaxies, Physics, [PHYS]Physics [physics], radio lines: ISM, ISM [galaxies], general [ISM], Astronomy and Astrophysics, Astronomy and Astrophysic, Astrophysics - Astrophysics of Galaxies, galaxies [radio lines], Interstellar medium, Radial velocity, Supernova, radio lines: galaxie, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), individual (M82) [galaxies], ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], galaxies: ISM
Abstract: Carbon radio recombination lines (RRLs) at low frequencies (, Comment: 6 pages, 5 figures, accepted for publication in ApJL
Published: 2014

34. The Radio Spectral Energy Distribution and Star Formation Rate Calibration in Galaxies

Author: Sharon E. Meidt, I. De Looze, Robert C. Kennicutt, D. D. Mulcahy, A. Damas-Segovia, M. Krause, Fatemeh Tabatabaei, Daniel A. Dale, Maud Galametz, Médéric Boquien, D. Calzetti, Ron Beck, G. Dumas, Eric J. Murphy, L. K. Hunt, Eva Schinnerer, Eric W. Pellegrini, Karin Sandstrom, Brent Groves, Alberto D. Bolatto, DEU, Kennicutt, Robert [0000-0001-5448-1821], and Apollo - University of Cambridge Repository
Subjects: Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Cosmic ray, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, NRAO PMN SURVEYS, 01 natural sciences, galaxies [infrared], law.invention, infrared: galaxies, surveys, SHAPLEY-AMES GALAXIES, law, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, NEARBY GALAXIES, SMALL-MAGELLANIC-CLOUD, machine-readable tables [surveys Supporting material], 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Physics, radio continuum: galaxies, MAGNETIC-FIELD STRUCTURE, Spectral index, ISM [galaxies], 010308 nuclear & particles physics, Star formation, Bolometer, NONTHERMAL RADIO, Astronomy and Astrophysics, Astrophysics - Astrophysics of Galaxies, Redshift, Galaxy, galaxies [radio continuum], Magnetic field, Physics and Astronomy, Space and Planetary Science, FAR-INFRARED/RADIO CORRELATION, galaxies: star formation, Astrophysics of Galaxies (astro-ph.GA), Spectral energy distribution, CONTINUUM SURVEY, star formation [galaxies], FORMATION RATE INDICATORS, SPIRAL GALAXIES, galaxies: ISM
Abstract: We study the spectral energy distribution (SED) of the radio continuum (RC) emission from the Key Insight in Nearby Galaxies Emitting in Radio (KINGFISHER) sample of nearby galaxies to understand the energetics and origin of this emission. Effelsberg multi-wavelength observations at 1.4, 4.8, 8.4, and 10.5 GHz combined with archive data allow us, for the first time, to determine the mid-RC (1–10 GHz, MRC) bolometric luminosities and further present calibration relations versus the monochromatic radio luminosities. The 1–10 GHz radio SED is fitted using a Bayesian Markov Chain Monte Carlo technique leading to measurements for the nonthermal spectral index ($S_{\nu}$ ~ $\nu$$^ {-\alpha_{nt}}$) and the thermal fraction ($f_{\text{th}}$) with mean values of $\alpha_{nt}$ = 0.97 ± 0.16 (0.79 ± 0.15 for the total spectral index) and $f_{\text{th}}$ = (10 ± 9)% at 1.4 GHz. The MRC luminosity changes over ~3 orders of magnitude in the sample, 4.3 $\times$ 10$^2$ $L_\odot$ < MRC < 3.9 $\times$ 10$^5$ $L_\odot$. The thermal emission is responsible for ~23% of the MRC on average. We also compare the extinction-corrected diagnostics of the star-formation rate (SFR) with the thermal and nonthermal radio tracers and derive the first star-formation calibration relations using the MRC radio luminosity. The nonthermal spectral index flattens with increasing SFR surface density, indicating the effect of the star-formation feedback on the cosmic-ray electron population in galaxies. Comparing the radio and IR SEDs, we find that the FIR-to-MRC ratio could decrease with SFR, due to the amplification of the magnetic fields in star-forming regions. This particularly implies a decrease in the ratio at high redshifts, where mostly luminous/star-forming galaxies are detected., F.S.T. acknowledges support by the German Research Foundation DFG via the grant TA 801/1-1 and the Spanish Ministry of Economy and Competitiveness(MINECO) under grant number AYA2013-41243-P. R.B. acknowledges financial support from DFG Research Unit FOR1254. D.D.M acknowledges support from ERCStG 307215 (LODESTONE).

35. The Radio Spectral Energy Distribution and Star-formation Rate Calibration in Galaxies.

Author: F. S. Tabatabaei, M. Galametz, K. Sandstrom, M. Boquien, D. Calzetti, R. C. Kennicutt, L. K. Hunt, I. De Looze, E. W. Pellegrini, E. Schinnerer, G. Dumas, S. Meidt, M. Krause, A. Damas-Segovia, R. Beck, E. J. Murphy, D. D. Mulcahy, B. Groves, A. Bolatto, and D. Dale
Subjects: INTERSTELLAR medium, SPECTRAL energy distribution, STAR formation, STELLAR evolution, CALIBRATION
Abstract: We study the spectral energy distribution (SED) of the radio continuum (RC) emission from the Key Insight in Nearby Galaxies Emitting in Radio (KINGFISHER) sample of nearby galaxies to understand the energetics and origin of this emission. Effelsberg multi-wavelength observations at 1.4, 4.8, 8.4, and 10.5 GHz combined with archive data allow us, for the first time, to determine the mid-RC (1–10 GHz, MRC) bolometric luminosities and further present calibration relations versus the monochromatic radio luminosities. The 1–10 GHz radio SED is fitted using a Bayesian Markov Chain Monte Carlo technique leading to measurements for the nonthermal spectral index () and the thermal fraction () with mean values of for the total spectral index) and = (10 ± 9)% at 1.4 GHz. The MRC luminosity changes over ∼3 orders of magnitude in the sample, MRC . The thermal emission is responsible for ∼23% of the MRC on average. We also compare the extinction-corrected diagnostics of the star-formation rate (SFR) with the thermal and nonthermal radio tracers and derive the first star-formation calibration relations using the MRC radio luminosity. The nonthermal spectral index flattens with increasing SFR surface density, indicating the effect of the star-formation feedback on the cosmic-ray electron population in galaxies. Comparing the radio and IR SEDs, we find that the FIR-to-MRC ratio could decrease with SFR, due to the amplification of the magnetic fields in star-forming regions. This particularly implies a decrease in the ratio at high redshifts, where mostly luminous/star-forming galaxies are detected. [ABSTRACT FROM AUTHOR]
Published: 2017
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36. Exploring diastolic pressure ratio to fractional flow reserve discordance and a hypothesis on tailoring diastolic pressure ratio cut-off values to improve diagnostic accuracy in the mid- and distal-LAD.

Author: Balfe C, Jacob B, Hickey N, Moore D, Mulcahy D, and Loo B
Abstract: Previous studies have identified a higher rate of discordance between non-hyperaemic pressure ratios and FFR in the LAD when compared to the other two coronary arteries. We hypothesised that in keeping with recently published data, we would identify a higher discordance rate between diastolic pressure ratio (DPR) and FFR in the LAD compared to the RCA or LCx. In our study, 12.7% of LAD lesions had discordant results compared with 2.4% of non-LAD lesions. This represents a statistically significant increased rate of discordance in LAD lesions compared to non-LAD lesions (p = 0.04986). Note was made of a tendency for non-proximal LAD lesions to be associated with false-positive DPR results in the borderline range (0.88 and 0.89). In a speculative, hypothesis generating post-hoc analysis, we found an improved diagnostic accuracy of DPR when the cut-off value for a positive DPR in the non-proximal LAD was changed to ≤0.87. It is fathomable that improvements in the diagnostic accuracy of DPR for FFR may be improved by tailoring DPR cut-offs to the location of the lesion assessed., Competing Interests: The authors report no relationships that could be construed as a conflict of interest., (© 2021 The Authors.)
Published: 2021
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37. Light scattering and random lasing in aqueous suspensions of hexagonal boron nitride nanoflakes.

Author: O'Brien SA, Harvey A, Griffin A, Donnelly T, Mulcahy D, Coleman JN, Donegan JF, and McCloskey D
Abstract: Liquid phase exfoliation allows large scale production of 2D materials in solution. The particles are highly anisotropic and strongly scatter light. While spherical particles can be accurately and precisely described by a single parameter-the radius, 2D nanoflakes, however, cannot be so easily described. We investigate light scattering in aqueous solutions of 2D hexagonal boron nitride nanoflakes in the single and multiple scattering regimes. In the single scattering regime, the anisotropic 2D materials show a much stronger depolarization of light when compared to spherical particles of similar size. In the multiple scattering regime, the scattering as a function of optical path for hexagonal boron nitride nanoflakes of a given lateral length was found to be qualitatively equivalent to scattering from spheres with the same diameter. We also report the presence of random lasing in high concentration suspensions of aqueous h-BN mixed with Rhodamine B dye. The h-BN works as a scattering agent and Rhodamine B as a gain medium for the process. We observed random lasing at 587 nm with a threshold energy of 0.8 mJ.
Published: 2017
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38. Nurse Triage in an Irish Out-of-hours General Practice Co-Operative.

Author: Mulcahy D, O'Callaghan C, and Hannigan A
Subjects: Child, Preschool, Humans, Ireland, Retrospective Studies, Telephone statistics & numerical data, After-Hours Care statistics & numerical data, Family Practice statistics & numerical data, Practice Patterns, Nurses' statistics & numerical data, Triage statistics & numerical data
Abstract: Specially trained triage nurses play a crucial role in the operation of out-of-hours GP co-operatives. This study aimed to establish the proportion of all patient contacts with the out-of-hours GP co-operative based in the Mid-West of Ireland (Shannondoc), which were managed by triage nurses. A retrospective, descriptive analysis was conducted on the database of contacts to the Shannondoc urgent, out-of-hours primary care co-operative. Of the 110,039 contacts to the service in 2013, 19,147 (17.4%) were classified as being managed by nurses and 14.2% were managed by nurse telephone triage alone. Twenty-four percent of the 19,147 calls managed by nurses involved children under six years. Triage nurses play an important role in administering safe medical advice over the phone. This has implications for the training of triage nurses and the future planning of urgent out-of-hours primary care services.
Published: 2017

39. The Global Genome Biodiversity Network (GGBN) Data Standard specification.

Author: Droege G, Barker K, Seberg O, Coddington J, Benson E, Berendsohn WG, Bunk B, Butler C, Cawsey EM, Deck J, Döring M, Flemons P, Gemeinholzer B, Güntsch A, Hollowell T, Kelbert P, Kostadinov I, Kottmann R, Lawlor RT, Lyal C, Mackenzie-Dodds J, Meyer C, Mulcahy D, Nussbeck SY, O'Tuama É, Orrell T, Petersen G, Robertson T, Söhngen C, Whitacre J, Wieczorek J, Yilmaz P, Zetzsche H, Zhang Y, and Zhou X
Subjects: Biodiversity, Databases, Nucleic Acid, Genome
Abstract: Genomic samples of non-model organisms are becoming increasingly important in a broad range of studies from developmental biology, biodiversity analyses, to conservation. Genomic sample definition, description, quality, voucher information and metadata all need to be digitized and disseminated across scientific communities. This information needs to be concise and consistent in today's ever-increasing bioinformatic era, for complementary data aggregators to easily map databases to one another. In order to facilitate exchange of information on genomic samples and their derived data, the Global Genome Biodiversity Network (GGBN) Data Standard is intended to provide a platform based on a documented agreement to promote the efficient sharing and usage of genomic sample material and associated specimen information in a consistent way. The new data standard presented here build upon existing standards commonly used within the community extending them with the capability to exchange data on tissue, environmental and DNA sample as well as sequences. The GGBN Data Standard will reveal and democratize the hidden contents of biodiversity biobanks, for the convenience of everyone in the wider biobanking community. Technical tools exist for data providers to easily map their databases to the standard.Database URL: http://terms.tdwg.org/wiki/GGBN_Data_Standard., (© The Author(s) 2016. Published by Oxford University Press.)
Published: 2016
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40. A rare case of cryptogenic stroke with an incidental finding of patent foramen ovale.

Author: Anglim B, Maher N, Cunningham O, Mulcahy D, Harbison J, and O'Connell M
Subjects: Adult, Female, Humans, Incidental Findings, Magnetic Resonance Imaging, Platelet Aggregation Inhibitors administration & dosage, Tomography, X-Ray Computed, Treatment Outcome, Aspirin administration & dosage, Brain Infarction diagnosis, Brain Infarction drug therapy, Brain Infarction etiology, Brain Infarction physiopathology, Foramen Ovale, Patent complications, Foramen Ovale, Patent diagnosis, Parietal Lobe pathology, Puerperal Disorders diagnosis, Puerperal Disorders drug therapy, Puerperal Disorders etiology, Puerperal Disorders physiopathology
Published: 2015

41. Osteochondroma development subsequent to traumatic hip dislocation.

Author: Laing AJ, Dillon JP, Suiluman B, and Mulcahy D
Subjects: Accidents, Traffic, Child, Female, Femoral Neoplasms diagnosis, Hip Dislocation diagnosis, Hip Injuries rehabilitation, Humans, Osteochondroma diagnosis, Treatment Outcome, Femoral Neoplasms etiology, Femoral Neoplasms rehabilitation, Hip Dislocation complications, Hip Dislocation rehabilitation, Hip Injuries complications, Hip Injuries diagnosis, Osteochondroma etiology, Osteochondroma rehabilitation
Published: 2008
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42. The use of uncemented extensively porous-coated femoral components in the management of Vancouver B2 and B3 periprosthetic femoral fractures.

Author: O'Shea K, Quinlan JF, Kutty S, Mulcahy D, and Brady OH
Subjects: Aged, 80 and over, Arthroplasty, Replacement, Hip instrumentation, Female, Humans, Male, Middle Aged, Prosthesis Design, Prosthesis Failure, Reoperation, Retrospective Studies, Treatment Outcome, Arthroplasty, Replacement, Hip methods, Femoral Fractures surgery, Hip Prosthesis
Abstract: We assessed the outcome of patients with Vancouver type B2 and B3 periprosthetic fractures treated with femoral revision using an uncemented extensively porous-coated implant. A retrospective clinical and radiographic assessment of 22 patients with a mean follow-up of 33.7 months was performed. The mean time from the index procedure to fracture was 10.8 years. There were 17 patients with a satisfactory result. Complications in four patients included subsidence in two, deep sepsis in one, and delayed union in one. Concomitant acetabular revision was required in 19 patients. Uncemented extensively porous-coated femoral stems incorporate distally allowing stable fixation. We found good early survival rates and a low incidence of nonunion using this implant.
Published: 2005
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43. Pasteurella multocida osteomyelitis following a dog bite.

Author: Mahapatra AN and Mulcahy D
Subjects: Animals, Hand Injuries etiology, Humans, Male, Middle Aged, Bites and Stings complications, Dogs, Osteomyelitis etiology, Pasteurella Infections etiology, Pasteurella multocida
Published: 2002
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44. Value of Mycobacterium tuberculosis fingerprinting as a tool in a rural state surveillance program.

Author: Dobbs KG, Lok KH, Bruce F, Mulcahy D, Benjamin WH, and Dunlap NE
Subjects: Adult, Alabama epidemiology, Contact Tracing, Female, Humans, Male, Middle Aged, Polymorphism, Restriction Fragment Length, Predictive Value of Tests, Risk Factors, Tuberculosis diagnosis, Tuberculosis transmission, DNA Fingerprinting, Disease Outbreaks, Mycobacterium tuberculosis genetics, Population Surveillance, Rural Population, Tuberculosis epidemiology
Abstract: Objective: This study demonstrates the value of Mycobacterium tuberculosis fingerprinting used in conjunction with traditional epidemiologic methods to identify smoldering outbreaks of tuberculosis in endemic areas where background rates of tuberculosis are high., Methods: IS6110 DNA fingerprinting was performed on isolates of M tuberculosis from verified cases of tuberculosis in Alabama from 1994 to 1998. A statewide database groups isolates into "clusters" and tracks them cumulatively over time. A large cluster was identified and was secondarily investigated using traditional epidemiologic methods., Results: Twenty-five isolates were found to be identical by fingerprinting analysis. Patients were living within 10 counties across the state, and 12 cases were localized to a single county. This represented an ongoing, statewide tuberculosis outbreak previously unrecognized by local and state health officials. Secondary investigation of the cases revealed the primary sites of transmission to be a correctional facility and two homeless shelters., Conclusions: Population surveillance using M tuberculosis fingerprinting was successfully utilized to detect a significant and smoldering tuberculosis outbreak. Measures are currently in place to identify and prevent further transmission in the involved locations.
Published: 2001
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45. Epidemiologic usefulness of spoligotyping for secondary typing of Mycobacterium tuberculosis isolates with low copy numbers of IS6110.

Author: Cronin WA, Golub JE, Magder LS, Baruch NG, Lathan MJ, Mukasa LN, Hooper N, Razeq JH, Mulcahy D, Benjamin WH, and Bishai WR
Subjects: Aged, Bacterial Typing Techniques, Humans, Mycobacterium tuberculosis genetics, Oligonucleotides analysis, Polymorphism, Restriction Fragment Length, Tuberculosis, Pulmonary microbiology, DNA Fingerprinting, DNA Transposable Elements genetics, Gene Dosage, Mycobacterium tuberculosis classification, Tuberculosis, Pulmonary epidemiology
Abstract: Restriction fragment length polymorphism (RFLP) analysis of IS6110 is commonly used to DNA fingerprint Mycobacterium tuberculosis. However, low-copy (< or =5) IS6110 M. tuberculosis strains are poorly differentiated, requiring secondary typing. When spoligotyping was used as the secondary method, only 13% of Maryland culture-positive tuberculosis (TB) patients with low-copy IS6110-spoligotyped clustered strains had epidemiologic linkages to another patient, compared to 48% of those with high-copy strains clustered by IS6110 alone (P < 0.01). Spoligotyping did not improve a population-based molecular epidemiologic study of recent TB transmission.
Published: 2001
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46. Statins and cardiovascular disease--major therapeutic advances but are we seizing the moment?

Author: Mulcahy D
Subjects: Cholesterol blood, Cholesterol, LDL blood, Humans, Myocardial Infarction blood, Myocardial Infarction epidemiology, Risk Factors, Anticholesteremic Agents therapeutic use, Cardiovascular Diseases prevention & control
Published: 2001
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47. Identification of a contaminating Mycobacterium tuberculosis strain with a transposition of an IS6110 insertion element resulting in an altered spoligotype.

Author: Benjamin WH Jr, Lok KH, Harris R, Brook N, Bond L, Mulcahy D, Robinson N, Pruitt V, Kirkpatrick DP, Kimerling ME, and Dunlap NE
Subjects: Bacterial Typing Techniques, Base Sequence, DNA, Intergenic genetics, Humans, Male, Middle Aged, Molecular Sequence Data, Oligonucleotides analysis, Polymerase Chain Reaction, Polymorphism, Restriction Fragment Length, Repetitive Sequences, Nucleic Acid genetics, Tuberculosis, Pulmonary microbiology, Bronchoscopes, DNA Transposable Elements, Equipment Contamination, Mycobacterium tuberculosis classification, Mycobacterium tuberculosis genetics, Tuberculosis, Pulmonary epidemiology
Abstract: Molecular fingerprinting with the IS6110 insertion sequence is useful for tracking transmission of Mycobacterium tuberculosis within a population or confirming specimen contamination in the laboratory or through instrumentation. Secondary typing with other molecular methods yields additional information as to the relatedness of strains with similar IS6110 fingerprints. Isolated, relatively rare, random events within the M. tuberculosis genome alter molecular fingerprinting patterns with any of the methods; therefore, strains which are different by two or more typing methods are usually not considered to be closely related. In this report, we describe two strains of M. tuberculosis, obtained from the same bronchoscope 2 days apart, that demonstrated unique molecular fingerprinting patterns by two different typing methods. They were closely linked through the bronchoscope by a traditional epidemiologic investigation. Genetic analysis of the two strains revealed that a single event, the transposition of an IS6110 insertion sequence in one of the strains, accounted for both the differences in the IS6110 pattern and the apparent deletion of a spacer in the spoligotype. This finding shows that a single event can change the molecular fingerprint of a strain in two different molecular typing systems, and thus, molecular typing cannot be the only means used to track transmission of this organism through a population. Traditional epidemiologic techniques are a necessary complement to molecular fingerprinting so that radical changes within the fingerprint pattern can be identified.
Published: 2001
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48. Trochanteric union in revision hip arthroplasty.

Author: Nicholson P, Mulcahy D, and Fenelon G
Subjects: Aged, Aged, 80 and over, Female, Humans, Male, Middle Aged, Reoperation, Wound Healing, Arthroplasty, Replacement, Hip, Femur surgery, Osteotomy adverse effects
Abstract: A total of 69 patients undergoing revision hip arthroplasty using a transtrochanteric approach who all had at least 1 previous transtrochanteric surgical approach. In 6 patients, it was the third time the trochanter was taken down, and in 2 patients, it was the fourth time. We believe this is the first review of trochanteric union in such a subgroup of patients. The mean age was 66 years (range, 46-82 years). Before revision, 49 of 69 patients (71%) had a united trochanter, whereas 20 of 69 (29%) had a pseudarthrosis. The overall pseudarthrosis rate decreased from 20 patients (29%) to 10 patients (14%) after revision surgery. The mean Harris hip score was 86 (range, 29-100). Repeated transtrochanteric osteotomy was not associated with any significant morbidity and did not affect the clinical outcome.
Published: 2001
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49. Evaluation of the role of pin fixation versus collar and cuff immobilisation in supracondylar fractures of the humerus in children.

Author: Kennedy JG, El Abed K, Soffe K, Kearns S, Mulcahy D, Condon F, Moore D, Dowling F, and Fogarty E
Subjects: Algorithms, Child, Child, Preschool, Evaluation Studies as Topic, Female, Follow-Up Studies, Fracture Fixation adverse effects, Fracture Fixation, Internal adverse effects, Fracture Fixation, Internal methods, Humans, Male, Bone Nails, Fracture Fixation methods, Humeral Fractures surgery, Elbow Injuries
Abstract: Long term results of children with supracondylar humeral fractures treated with manipulation and strapping and manipulation followed by pin fixation were evaluated. Forty patients were regarded as Gartland type II injuries. 33 of these were treated with closed reduction and collar and cuff immobilisation and 7 with closed reduction and percutaneous pinning. Two cases of cubitus varus were reported one from each treatment modality. Forty-four patients were included as Gartland type III injuries. Of these 14 were treated with closed reduction and collar and cuff immobilisation, 25 with closed reduction and percutaneous pinning and five with open reduction and pinning. There were two cases of cubitus varus and one case of cubitus valgus following pin fixation. In addition one case of extension lag and one significant ulnar nerve neurapraxia was recorded following pin fixation. One case of cubitus varus was seen following manipulation and collar and cuff treatment. There was no statistical difference between either treatment modality in terms of predicting a better outcome (p0.05). We conclude that pin fixation has no advantages over simple immobilisation in certain Gartland II and III type injuries. Although pin fixation is beneficial in unstable injuries collar and cuff immobilisation continues to have an important role in the treatment of stable supracondylar fractures.
Published: 2000
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50. "Circadian" variation in cardiovascular events and implications for therapy?

Author: Mulcahy D
Subjects: Clinical Trials as Topic, Humans, Time Factors, Acute Disease epidemiology, Cardiovascular Agents administration & dosage, Cardiovascular Diseases drug therapy, Cardiovascular Physiological Phenomena, Circadian Rhythm physiology
Abstract: For many years, it was thought that acute cardiovascular events occurred in a random fashion. However, over the past 13 years or so, a significant amount of research, both retrospective and prospective, has shown that there is an excess of ischaemic activity, arrhythmic activity and acute cardiovascular events in the first few hours after waking and commencing activity. This excess may well be at least partly linked to the known physiological changes which occur after waking, including a surge in heart rate, blood pressure and catecholamine release, activation of the renin-angiotensin system, an increase in platelet aggregability on assuming the upright posture, and the final trough in the fibrinolytic system. Because of the relatively short half-life and duration of the therapeutic effect (<24 h) of many anti-ischaemic and anti-arrhythmic agents, it is likely that single day agents taken in the morning will have reached subtherapeutic levels at the time of waking and commencing activity the following morning. As many patients do not take their daily (morning) medication immediately on rising, and allowing for time for adsorption, it is likely that, despite our knowledge of "circadian variations" in both physiological responses and pathophysiological events in the morning waking hours, patients are in fact at least protection at this particular high-risk time of the 24 h day. With our knowledge about when events are more likely to happen, we should consider carefully the timing of administration of medications, having factored in the likely length of therapeutic effect in each instance. It is likely that the almost universal inability to demonstrate prognostic benefit with many anti-ischaemic and anti-arrhythmic agents to date relates at least in part to a lack of appropriate "protection" at the time of apparent greatest risk in the patient with cardiovascular disease. Intelligent prescribing might indeed improve outcome, and even in the absence of proof on this regard, it would seem appropriate that we at least strive to achieve such an outcome.
Published: 1999
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