Search

Your search keyword '"Hoeft Matthias"' showing total 80 results
Start Over Author "Hoeft Matthias"
80 results on '"Hoeft Matthias"'

51. Realising the LOFAR Two-Metre Sky Survey

Author

Drabent, Alexander, Hoeft, Matthias, Dettmar, Ralf-Jürgen, Brüggen, Marcus, Schwarz, Dominik J., Mechev, Alex B., Oonk, J. B. Raymond, Shimwell, Timothy W., Sweijen, Frits, Danezi, Anatoli, Schrijvers, Coen, Manzano, Cristina, and Tsigenov, Oleg

Abstract

The new generation of high-resolution broad-band radio telescopes, like the Low Frequency Array (LOFAR), produces, depending on the level of compression, between 1 to 10 TB of data per hour after correlation. Such a large amount of scientific data demand powerful computing resources and efficient data handling strategies to be mastered. The LOFAR Two-metre Sky Survey (LoTSS) is a Key Science Project (KSP) of the LOFAR telescope. It aims to map the entire northern hemisphere at unprecedented sensitivity and resolution. The survey consist of 3 168 pointings, requiring about 30 PBytes of storage space. As a member of the German Long Wavelength Consortium (GLOW) the Forschungszentrum Jülich (FZJ) stores in the Long Term Archive (LTA) about 50% of all LoTSS observations conducted to date. In collaboration with SURFsara in Amsterdam we developed service tools that enables the KSP to process LOFAR data stored in the LTA at the Jülich Supercomputing Centre (JSC) in an automated and robust fashion. Through our system more than 500 out of 800 existing LoTSS observationshave already been processed with the prefactor pipeline. This pipeline calibrates the direction-independent instrumental and ionospheric effects and furthermore reduces the data size significantly. For continuum imaging, this processing pipeline is the standard pipeline that is executed before more advanced processing and image reconstruction methods are applied.

Published
2020

52. Magnetism science with the square kilometre array

Author

The Dunlap Family, University of Toronto, Natural Sciences and Engineering Research Council of Canada, Canada Research Chairs, Ministerio de Economía y Competitividad (España), CSIC - Instituto de Astrofísica de Andalucía (IAA), Federal Ministry of Education and Research (Germany), Department of Science and Technology (India), National Key Research and Development Program (China), National Research Council of Canada, University of Minnesota, European Research Council, European Commission, Ministero dell'Istruzione, dell'Università e della Ricerca, National Science Foundation (US), Agilent Foundation, Ministerio de Ciencia, Innovación y Universidades (España), Agencia Estatal de Investigación (España), Heald, George, Mao, Sui Ann, Vacca, Valentina, Akahori, Takuya, Damas-Segovia, Ancor, Gaensler, B. M., Hoeft, Matthias, Agudo, Iván, Basu, Aritra, Beck, Rainer, Birkinshaw, Mark, Bonafede, Annalisa, Bourke, Tyler L., Bracco, Andrea, Carretti, Ettore, Feretti, Luigina, Girart, Josep Miquel, Govoni, Federica, Green, James A., Han, JinLin, Haverkorn, Marijke, Horellou, Cathy, Johnston-Hollitt, Melanie, Kothes, Roland, Landecker, Tom, Nikiel-Wroczyński, Błażej, O’Sullivan, Shane P., Padovani, Marco, Poidevin, Frédérick, Pratley, Luke, Regis, Marco, Riseley, Christopher John, Robishaw, Tim, Rudnick, Lawrence, Sobey, Charlotte, Stil, Jeroen M., Sun, Xiaohui, Sur, Sharanya, Taylor, A. Russ, Thomson, Alec, Van Eck, Cameron L., Vazza, Franco, West, Jennifer L., the SKA Magnetism Science Working Group, The Dunlap Family, University of Toronto, Natural Sciences and Engineering Research Council of Canada, Canada Research Chairs, Ministerio de Economía y Competitividad (España), CSIC - Instituto de Astrofísica de Andalucía (IAA), Federal Ministry of Education and Research (Germany), Department of Science and Technology (India), National Key Research and Development Program (China), National Research Council of Canada, University of Minnesota, European Research Council, European Commission, Ministero dell'Istruzione, dell'Università e della Ricerca, National Science Foundation (US), Agilent Foundation, Ministerio de Ciencia, Innovación y Universidades (España), Agencia Estatal de Investigación (España), Heald, George, Mao, Sui Ann, Vacca, Valentina, Akahori, Takuya, Damas-Segovia, Ancor, Gaensler, B. M., Hoeft, Matthias, Agudo, Iván, Basu, Aritra, Beck, Rainer, Birkinshaw, Mark, Bonafede, Annalisa, Bourke, Tyler L., Bracco, Andrea, Carretti, Ettore, Feretti, Luigina, Girart, Josep Miquel, Govoni, Federica, Green, James A., Han, JinLin, Haverkorn, Marijke, Horellou, Cathy, Johnston-Hollitt, Melanie, Kothes, Roland, Landecker, Tom, Nikiel-Wroczyński, Błażej, O’Sullivan, Shane P., Padovani, Marco, Poidevin, Frédérick, Pratley, Luke, Regis, Marco, Riseley, Christopher John, Robishaw, Tim, Rudnick, Lawrence, Sobey, Charlotte, Stil, Jeroen M., Sun, Xiaohui, Sur, Sharanya, Taylor, A. Russ, Thomson, Alec, Van Eck, Cameron L., Vazza, Franco, West, Jennifer L., and the SKA Magnetism Science Working Group

Abstract

The Square Kilometre Array (SKA) will answer fundamental questions about the origin, evolution, properties, and influence of magnetic fields throughout the Universe. Magnetic fields can illuminate and influence phenomena as diverse as star formation, galactic dynamics, fast radio bursts, active galactic nuclei, large-scale structure, and dark matter annihilation. Preparations for the SKA are swiftly continuing worldwide, and the community is making tremendous observational progress in the field of cosmic magnetism using data from a powerful international suite of SKA pathfinder and precursor telescopes. In this contribution, we revisit community plans for magnetism research using the SKA, in light of these recent rapid developments. We focus in particular on the impact that new radio telescope instrumentation is generating, thus advancing our understanding of key SKA magnetism science areas, as well as the new techniques that are required for processing and interpreting the data. We discuss these recent developments in the context of the ultimate scientific goals for the SKA era.

Published
2020

53. Fast magnetic field amplification in distant galaxy clusters

Author

Di Gennaro, Gabriella, primary, van Weeren, Reinout J., additional, Brunetti, Gianfranco, additional, Cassano, Rossella, additional, Brüggen, Marcus, additional, Hoeft, Matthias, additional, Shimwell, Timothy W., additional, Röttgering, Huub J. A., additional, Bonafede, Annalisa, additional, Botteon, Andrea, additional, Cuciti, Virginia, additional, Dallacasa, Daniele, additional, de Gasperin, Francesco, additional, Domínguez-Fernández, Paola, additional, Enßlin, Torsten A., additional, Gastaldello, Fabio, additional, Mandal, Soumyajit, additional, Rossetti, Mariachiara, additional, and Simionescu, Aurora, additional

Published
2020
Full Text
View/download PDF

58. A LOFAR DETECTION OF THE LOW-MASS YOUNG STAR T TAU AT 149 MHz

Author

Coughlan, Colm P., primary, Ainsworth, Rachael E., additional, Eislöffel, Jochen, additional, Hoeft, Matthias, additional, Drabent, Alexander, additional, Scaife, Anna M. M., additional, Ray, Tom P., additional, Bell, Martin E., additional, Broderick, Jess W., additional, Corbel, Stéphane, additional, Grießmeier, Jean-Mathias, additional, van der Horst, Alexander J., additional, van Leeuwen, Joeri, additional, Markoff, Sera, additional, Pietka, Malgorzata, additional, Stewart, Adam J., additional, Wijers, Ralph A. M. J., additional, and Zarka, Philippe, additional

Published
2017
Full Text
View/download PDF

61. The widest frequency radio relic spectra: observations from 150 MHz to 30 GHz

Author

Stroe, Andra, primary, Shimwell, Timothy, additional, Rumsey, Clare, additional, van Weeren, Reinout, additional, Kierdorf, Maja, additional, Donnert, Julius, additional, Jones, Thomas W., additional, Röttgering, Huub J. A., additional, Hoeft, Matthias, additional, Rodríguez-Gonzálvez, Carmen, additional, Harwood, Jeremy J., additional, and Saunders, Richard D. E., additional

Published
2015
Full Text
View/download PDF

62. LOFAR and APERTIF Surveys of the Radio Sky: Probing Shocks and Magnetic Fields in Galaxy Clusters: Probing Shocks and Magnetic Fields in Galaxy Clusters

Author

Rottgering, Huub, Afonso, Jose, Barthel, Peter, Batejat, Fabien, Best, Philip, Bonafede, Annalisa, Brueggen, Marcus, Brunetti, Gianfranco, Chyzy, Krzysztof, Conway, John, De Gasperin, Francesco, Ferrari, Chiara, Haverkorn, Marijke, Heald, George, Hoeft, Matthias, Jackson, Neal, Jarvis, Matt, Ker, Louise, Lehnert, Matt, Macario, Giulia, McKean, John, Miley, George, Morganti, Raffaella, Oosterloo, Tom, Orru, Emanuela, Pizzo, Roberto, Rafferty, David, Shulevski, Alexander, Tasse, Cyril, van Bemmel, Ilse, van der Tol, Bas, van Weeren, Reinout, Verheijen, Marc, White, Glenn, Wise, Michael, Astronomy, and Kapteyn Astronomical Institute

Subjects
radio continuum: galaxies, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, 1.4 GHZ, Astrophysics::Cosmology and Extragalactic Astrophysics, radio telescopes, EMISSION, ABELL 2256, HALOS, Astrophysics::Galaxy Astrophysics, Galaxies: clusters: general, intracluster medium
Abstract

At very low frequencies, the new pan-European radio telescope LOFAR is opening the last unexplored window of the electromagnetic spectrum for astrophysical studies. The revolutionary APERTIF- phased arrays that are about to be installed on the Westerbork radio telescope (WSRT) will dramatically increase the survey speed for the WSRT. Combined surveys with these two facilities will deeply chart the northern sky over almost two decades in radio frequency from ˜15 up to 1400 MHz. Here we briefly describe some of the capabilities of these new facilities and what radio surveys are planned to study fun-damental issues related to the formation and evolution of galaxies and clusters of galaxies. In the second part we briefly review some recent observational results directly showing that diffuse radio emission in clusters traces shocks due to cluster mergers. As these diffuse radio sources are relatively bright at low frequencies, LOFAR should be able to detect thousands of such sources up to the epoch of cluster formation. This will allow addressing many question about the origin and evolution of shocks and magnetic fields in clusters. At the end we briefly review some of the first and very preliminary LOFAR results on clusters.

Published
2011

63. Spectral and morphological signatures of cluster merger shocks:CIZA J2242.8+5301

Author

Stroe, Andra, van Weeren, Reinout J., Sobral, David, Rumsey, Clare, Intema, Huib T., Röttgering, Huub J. A., Harwood, Jeremy J., Saunders, Richard, Brüggen, Marcus, Hoeft, Matthias, Stroe, Andra, van Weeren, Reinout J., Sobral, David, Rumsey, Clare, Intema, Huib T., Röttgering, Huub J. A., Harwood, Jeremy J., Saunders, Richard, Brüggen, Marcus, and Hoeft, Matthias

Abstract

The CIZA J2242.8+5301 cluster hosts an extraordinary, narrow, Mpc-wide, diffuse patch of radio emission tracing travelling shock waves, called a relic. We perform a multi-wavelength of observations of the cluster. We discover radio spectral steepening and increasing spectral curvature in the shock downstream area, indicative of emission produced by spectrally-aged electrons, following a JP ageing model. The curved integrated spectrum towards $16$ GHz challenges the favoured relic formation model. Further, we find a boosting the number density of H$\alpha$ emitters by a factor of $10$, possibly caused by interactions of the galaxies with the shock wave.

Published
2014

64. The widest frequency radio relic spectra: observations from 150 MHz to 30 GHz.

Author

Stroe, Andra, Shimwell, Timothy, Rumsey, Clare, Van Weeren, Reinout, Kierdorf, Maja, Donnert, Julius, Jones, Thomas W., Röttgering, Huub J. A., Hoeft, Matthias, Rodríguez-Gonzálvez, Carmen, Harwood, Jeremy J., and Saunders, Richard D. E.

Subjects
SYNCHROTRONS, PARTICLE accelerators, SHOCK waves, AERODYNAMICS, ELECTRONS
Abstract

Radio relics are patches of diffuse synchrotron radio emission that trace shock waves. Relics are thought to form when intracluster medium electrons are accelerated by cluster mergerinduced shock waves through the diffusive shock acceleration mechanism. In this paper, we present observations spanning 150 MHz to 30 GHz of the 'Sausage' and 'Toothbrush' relics from the Giant Metrewave and Westerbork telescopes, the Karl G. Jansky Very Large Array, the Effelsberg telescope, the Arcminute Microkelvin Imager and Combined Array for Research in Millimeter-wave Astronomy.We detect both relics at 30 GHz, where the previous highest frequency detection was at 16 GHz. The integrated radio spectra of both sources clearly steepen above 2 GHz, at the ≳6σ significance level, supporting the spectral steepening previously found in the 'Sausage' and the Abell 2256 relic. Our results challenge the widely adopted simple formation mechanism of radio relics and suggest more complicated models have to be developed that, for example, involve re-acceleration of aged seed electrons. [ABSTRACT FROM AUTHOR]

Published
2016
Full Text
View/download PDF

67. The fossil phase in the life of a galaxy group

Author

von Benda-Beckmann, Alexander M., primary, D'Onghia, Elena, additional, Gottlöber, Stefan, additional, Hoeft, Matthias, additional, Khalatyan, Arman, additional, Klypin, Anatoly, additional, and Müller, Volker, additional

Published
2008
Full Text
View/download PDF

70. Dwarf Galaxies in Voids: DarkMatter Halos and Gas Cooling.

Author

Hoeft, Matthias and Gottlöber, Stefan

Subjects
DWARF galaxies, DARK matter, GAS air conditioning, GALAXY clusters, ULTRAVIOLET astronomy, BARYONS
Abstract

Galaxy surveys have shown that luminous galaxies are mainly distributed in large filaments and galaxy clusters. The remaining large volumes are virtually devoid of luminous galaxies. This is in concordance with the formation of the large-scale structure in the universe as derived from cosmological simulations. However, the numerical results indicate that cosmological voids are abundantly populated with dark matter haloes which may in principle host dwarf galaxies. Observational efforts have in contrast revealed that voids are apparently devoid of dwarf galaxies. We investigate the formation of dwarf galaxies in voids by hydrodynamical cosmological simulations. Due to the cosmic ultraviolet background radiation low-mass haloes show generally a reduced baryon fraction. We determine the characteristic mass below which dwarf galaxies are baryon deficient. We show that the circular velocity below which the accretion of baryons is suppressed is approximately 40 km s-1. The suppressed baryon accretion is caused by the photo-heating due to the UV background. We set up a spherical halo model and show that the effective equation of the state of the gas in the periphery of dwarf galaxies determines the characteristic mass. This implies that any process which heats the gas around dwarf galaxies increases the characteristic mass and thus reduces the number of observable dwarf galaxies. [ABSTRACT FROM AUTHOR]

Published
2010
Full Text
View/download PDF

71. Radio signature of cosmological structure formation shocks.

Author

Hoeft, Matthias and Brüggen, Marcus

Subjects
*SHOCK waves, *SUPERNOVA remnants, *STAR formation, *SYNCHROTRON radiation, *METAPHYSICAL cosmology
Abstract

In the course of the formation of cosmological structures, large shock waves are generated in the intracluster medium (ICM). In analogy to processes in supernova remnants, these shock waves may generate a significant population of relativistic electrons which, in turn, produce observable synchrotron emission. The extended radio relics found at the periphery of several clusters and possibly also a fraction of radio halo emission may have this origin. Here, we derive an analytic expression for (i) the total radio power in the downstream region of a cosmological shock wave, and (ii) the width of the radio-emitting region. These expressions predict a spectral slope close to −1 for strong shocks. Moderate shocks, such as those produced in mergers between clusters of galaxies, lead to a somewhat steeper spectrum. Moreover, we predict an upper limit for the radio power of cosmological shocks. Comparing our results to the radio relics in Abell 115, 2256 and 3667, we conclude that the magnetic field in these relics is typically at a level of 0.1 μG. Magnetic fields in the ICM are presumably generated by the shocks themselves; this allows us to calculate the radio emission as a function of the cluster temperature. The resulting emissions agree very well with the radio power–temperature relation found for cluster haloes. Finally, we show that cosmic accretion shocks generate less radio emission than merger shock waves. The latter may, however, be detected with upcoming radio telescopes. [ABSTRACT FROM AUTHOR]

Published
2007
Full Text
View/download PDF

72. Wakes of ram-pressure-stripped disc galaxies.

Author

Roediger, Elke, Brüggen, Marcus, and Hoeft, Matthias

Subjects
SPIRAL galaxies, GALAXIES, ASTRONOMY, OSCILLATIONS, FLUCTUATIONS (Physics), VIBRATION (Mechanics)
Abstract

Spiral galaxies that move through the intracluster medium (ICM) lose a substantial amount of their gas discs due to ram-pressure stripping. The recent observations of NGC 4388 by Oosterloo & van Gorkom reveal a tail of stripped gas of ∼100 kpc behind the source galaxy. We present first 3D hydrodynamical simulations of the evolution of such ram-pressure-stripped tails. We find that if the ICM wind does not vary significantly over a period of a few 100 Myr, subsonic galaxies produce a tail with regular features similar to a von Karman vortex street. In this case, the tail widens systematically by about 45 kpc per 100 kpc distance behind the source galaxy. The widening rate is independent of the galaxy's inclination for a large range of inclinations. For supersonic galaxies, the tail is more irregular than for subsonic ones. The tail observed for NGC 4388 is narrower than the tails in our simulations. Reasons for this difference may be a time-dependent ram pressure or additional physical processes such as heat conduction or viscosity. In addition, we conclude that the observed S-shape of this tail is not due to von Karman oscillations. Finally, we discuss implications for the distribution of metals in the ICM due to ram-pressure stipping. [ABSTRACT FROM AUTHOR]

Published
2006
Full Text
View/download PDF

73. Radio relics in a cosmological cluster merger simulation.

Author

Hoeft, Matthias, Brüggen, Marcus, and Yepes, Gustavo

Subjects
*GALAXY clusters, *PLASMA astrophysics, *RADIO astronomy, *HYDRODYNAMICS, *SYNCHROTRON radiation, *METAPHYSICAL cosmology
Abstract

Motivated by the discovery of a number of radio relics we investigate the fate of fossil radio plasma during a merger of clusters of galaxies using cosmological smoothed-particle hydrodynamics simulations. Radio relics are extended, steep-spectrum radio sources that do not seem to be associated with a host galaxy. One scenario whereby these relics form has been proposed by Enßlin & Gobal-Krishna and proceeds via the compression of fossil radio plasma during a merger between clusters. The ensuing compression of the plasma can lead to a substantial increase in synchrotron luminosity and this appears as a radio relic. Our simulations show that relics are most likely found at the periphery of the cluster at the positions of the outgoing merger shock waves. Relics are expected to be very rare in the centre of the cluster where the lifetime of relativistic electrons is short and shock waves are weaker than in the cooler, peripheral regions of the cluster. These predictions can soon be tested with upcoming low-frequency radio telescopes. [ABSTRACT FROM AUTHOR]

Published
2004
Full Text
View/download PDF

74. A LOFAR observation of ionospheric scintillation from two simultaneous travelling ionospheric disturbances

Author

Fallows, Richard A., Forte, Biagio, Astin, Ivan, Allbrook, Tom, Arnold, Alex, Wood, Alan, Dorrian, Gareth, Mevius, Maaijke, Rothkaehl, Hanna, Matyjasiak, Barbara, Krankowski, Andrzej, Anderson, James M., Asgekar, Ashish, Avruch, I. Max, Bentum, Mark, Bisi, Mario M., Butcher, Harvey R., Ciardi, Benedetta, Dabrowski, Bartosz, Damstra, Sieds, De Gasperin, Francesco, Duscha, Sven, Eislöffel, Jochen, Franzen, Thomas M. O., Garrett, Michael A., Grießmeier, Jean-Matthias, Gunst, André W., Hoeft, Matthias, Hörandel, Jörg R., Iacobelli, Marco, Intema, Huib T., Koopmans, Leon V. E., Maat, Peter, Mann, Gottfried, Nelles, Anna, Paas, Harm, Pandey, Vishambhar N., Reich, Wolfgang, Rowlinson, Antonia, Ruiter, Mark, Schwarz, Dominik J., Serylak, Maciej, Shulevski, Aleksander, Smirnov, Oleg M., Soida, Marian, Steinmetz, Matthias, Thoudam, Satyendra, Toribio, M. Carmen, Van Ardenne, Arnold, Van Bemmel, Ilse M., Van Der Wiel, Matthijs H. D., Van Haarlem, Michiel P., Vermeulen, René C., Vocks, Christian, Wijers, Ralph A. M. J., Wucknitz, Olaf, Zarka, Philippe, and Zucca, Pietro

Subjects
13. Climate action
Abstract

Journal of space weather and space climate 10, 10 (2020). doi:10.1051/swsc/2020010, This paper presents the results from one of the first observations of ionospheric scintillation taken using the Low-Frequency Array (LOFAR). The observation was of the strong natural radio source Cassiopeia A, taken overnight on 18–19 August 2013, and exhibited moderately strong scattering effects in dynamic spectra of intensity received across an observing bandwidth of 10–80 MHz. Delay-Doppler spectra (the 2-D FFT of the dynamic spectrum) from the first hour of observation showed two discrete parabolic arcs, one with a steep curvature and the other shallow, which can be used to provide estimates of the distance to, and velocity of, the scattering plasma. A cross-correlation analysis of data received by the dense array of stations in the LOFAR “core” reveals two different velocities in the scintillation pattern: a primary velocity of ~20–40 ms$^{−1}$ with a north-west to south-east direction, associated with the steep parabolic arc and a scattering altitude in the F-region or higher, and a secondary velocity of ~110 ms$^{−1}$ with a north-east to south-west direction, associated with the shallow arc and a scattering altitude in the D-region. Geomagnetic activity was low in the mid-latitudes at the time, but a weak sub-storm at high latitudes reached its peak at the start of the observation. An analysis of Global Navigation Satellite Systems (GNSS) and ionosonde data from the time reveals a larger-scale travelling ionospheric disturbance (TID), possibly the result of the high-latitude activity, travelling in the north-west to south-east direction, and, simultaneously, a smaller-scale TID travelling in a north-east to south-west direction, which could be associated with atmospheric gravity wave activity. The LOFAR observation shows scattering from both TIDs, at different altitudes and propagating in different directions. To the best of our knowledge this is the first time that such a phenomenon has been reported., Published by EDP Sciences, Les Ulis

75. Spectral and morphological signatures of cluster merger shocks: CIZA J2242.8+5301

Author

Stroe, Andra, Weeren, Reinout J., Sobral, David, Rumsey, Clare, Intema, Huib T., Röttgering, Huub J. A., Jeremy Harwood, Saunders, Richard, Brüggen, Marcus, and Hoeft, Matthias

Subjects
Cosmology and Nongalactic Astrophysics (astro-ph.CO), Astrophysics::High Energy Astrophysical Phenomena, Astrophysics of Galaxies (astro-ph.GA), FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics - Astrophysics of Galaxies, Astrophysics::Galaxy Astrophysics, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

The CIZA J2242.8+5301 cluster hosts an extraordinary, narrow, Mpc-wide, diffuse patch of radio emission tracing travelling shock waves, called a relic. We perform a multi-wavelength of observations of the cluster. We discover radio spectral steepening and increasing spectral curvature in the shock downstream area, indicative of emission produced by spectrally-aged electrons, following a JP ageing model. The curved integrated spectrum towards $16$ GHz challenges the favoured relic formation model. Further, we find a boosting the number density of H$\alpha$ emitters by a factor of $10$, possibly caused by interactions of the galaxies with the shock wave., Comment: 4 pages, 2 figures, to appear in the proceedings of the conference `The Metre Wavelength Sky: Celebrating 50 years of Radio Astronomy at TIFR'

77. The fossil phase in the life of a galaxy group

Author

Von Benda-Beckmann, Alexander M., D'Onghia, Elena, Gottlöber, Stefan, Hoeft, Matthias, Khalatyan, Arman, Klypin, Anatoly, Müller, Volker, Von Benda-Beckmann, Alexander M., D'Onghia, Elena, Gottlöber, Stefan, Hoeft, Matthias, Khalatyan, Arman, Klypin, Anatoly, and Müller, Volker

Abstract

We investigate the origin and evolution of fossil groups in a concordance ΛCDM cosmological simulation. We consider haloes with masses between 1 × 1013 and 5 × 1013h−1M⊙, and study the physical mechanisms that lead to the formation of the large gap in magnitude between the brightest and the second most bright group member, which is typical for these fossil systems. Fossil groups are found to have high dark matter concentrations, which we can relate to their early formation time. The large magnitude gaps arise after the groups have built up half of their final mass, due to merging of massive group members. We show that the existence of fossil systems is primarily driven by the relatively early infall of massive satellites, and that we do not find a strong environmental dependence for these systems. In addition, we find tentative evidence for fossil group satellites falling in on orbits with typically lower angular momentum, which might lead to a more efficient merger on to the host. We find a population of groups at higher redshifts that go through a ‘fossil phase': a stage where they show a large magnitude gap, which is terminated by renewed infall from their environment

78. LOFAR and APERTIF Surveys of the radio sky: probing shocks and magnetic fields in galaxy clusters

Author

Röttgering, Huub, Afonso, Jose, Barthel, Peter, Batejat, Fabien, Best, Philip, Bonafede, Annalisa, Brüggen, Marcus, Brunetti, Gianfranco, Chyży, Krzysztof, Conway, John, Gasperin, Francesco De, Ferrari, Chiara, Haverkorn, Marijke, Heald, George, Hoeft, Matthias, Jackson, Neal, Jarvis, Matt, Ker, Louise, Lehnert, Matt, Macario, Giulia, McKean, John, Miley, George, Morganti, Raffaella, Oosterloo, Tom, Orrù, Emanuela, Pizzo, Roberto, Rafferty, David, Shulevski, Alexander, Tasse, Cyril, Bemmel, Ilse van, Tol, Bas, Weeren, Reinout, Verheijen, Marc, White, Glenn, Wise, Michael, Röttgering, Huub, Afonso, Jose, Barthel, Peter, Batejat, Fabien, Best, Philip, Bonafede, Annalisa, Brüggen, Marcus, Brunetti, Gianfranco, Chyży, Krzysztof, Conway, John, Gasperin, Francesco De, Ferrari, Chiara, Haverkorn, Marijke, Heald, George, Hoeft, Matthias, Jackson, Neal, Jarvis, Matt, Ker, Louise, Lehnert, Matt, Macario, Giulia, McKean, John, Miley, George, Morganti, Raffaella, Oosterloo, Tom, Orrù, Emanuela, Pizzo, Roberto, Rafferty, David, Shulevski, Alexander, Tasse, Cyril, Bemmel, Ilse van, Tol, Bas, Weeren, Reinout, Verheijen, Marc, White, Glenn, and Wise, Michael

Abstract

At very low frequencies, the new pan-European radio telescope LOFAR is opening the last unexplored window of the electromagnetic spectrum for astrophysical studies. The revolutionary APERTIFphased arrays that are about to be installed on the Westerbork radio telescope (WSRT) will dramatically increase the survey speed for the WSRT. Combined surveys with these two facilities will deeply chart the northern sky over almost two decades in radio frequency from ∼15 up to 1400 MHz. Here we briefly describe some of the capabilities of these new facilities and what radio surveys are planned to study fun-damental issues related to the formation and evolution of galaxies and clusters of galaxies. In the second part we briefly review some recent observational results directly showing that diffuse radio emission in clusters traces shocks due to cluster mergers. As these diffuse radio sources are relatively bright at low frequencies, LOFAR should be able to detect thousands of such sources up to the epoch of cluster formation. This will allow addressing many question about the origin and evolution of shocks and magnetic fields in clusters. At the end we briefly review some of the first and very preliminary LOFAR results on clusters.

79. LOFAR and APERTIF Surveys of the radio sky: probing shocks and magnetic fields in galaxy clusters

Author

Röttgering, Huub, Afonso, Jose, Barthel, Peter, Batejat, Fabien, Best, Philip, Bonafede, Annalisa, Brüggen, Marcus, Brunetti, Gianfranco, Chyży, Krzysztof, Conway, John, Gasperin, Francesco De, Ferrari, Chiara, Haverkorn, Marijke, Heald, George, Hoeft, Matthias, Jackson, Neal, Jarvis, Matt, Ker, Louise, Lehnert, Matt, Macario, Giulia, McKean, John, Miley, George, Morganti, Raffaella, Oosterloo, Tom, Orrù, Emanuela, Pizzo, Roberto, Rafferty, David, Shulevski, Alexander, Tasse, Cyril, Bemmel, Ilse van, Tol, Bas, Weeren, Reinout, Verheijen, Marc, White, Glenn, Wise, Michael, Röttgering, Huub, Afonso, Jose, Barthel, Peter, Batejat, Fabien, Best, Philip, Bonafede, Annalisa, Brüggen, Marcus, Brunetti, Gianfranco, Chyży, Krzysztof, Conway, John, Gasperin, Francesco De, Ferrari, Chiara, Haverkorn, Marijke, Heald, George, Hoeft, Matthias, Jackson, Neal, Jarvis, Matt, Ker, Louise, Lehnert, Matt, Macario, Giulia, McKean, John, Miley, George, Morganti, Raffaella, Oosterloo, Tom, Orrù, Emanuela, Pizzo, Roberto, Rafferty, David, Shulevski, Alexander, Tasse, Cyril, Bemmel, Ilse van, Tol, Bas, Weeren, Reinout, Verheijen, Marc, White, Glenn, and Wise, Michael

Abstract

At very low frequencies, the new pan-European radio telescope LOFAR is opening the last unexplored window of the electromagnetic spectrum for astrophysical studies. The revolutionary APERTIFphased arrays that are about to be installed on the Westerbork radio telescope (WSRT) will dramatically increase the survey speed for the WSRT. Combined surveys with these two facilities will deeply chart the northern sky over almost two decades in radio frequency from ∼15 up to 1400 MHz. Here we briefly describe some of the capabilities of these new facilities and what radio surveys are planned to study fun-damental issues related to the formation and evolution of galaxies and clusters of galaxies. In the second part we briefly review some recent observational results directly showing that diffuse radio emission in clusters traces shocks due to cluster mergers. As these diffuse radio sources are relatively bright at low frequencies, LOFAR should be able to detect thousands of such sources up to the epoch of cluster formation. This will allow addressing many question about the origin and evolution of shocks and magnetic fields in clusters. At the end we briefly review some of the first and very preliminary LOFAR results on clusters.

Full Text
View/download PDF

80. Spectral and morphological signatures of cluster merger shocks: CIZA J2242.8+5301

Author

Stroe, Andra, Weeren, Reinout J van, Sobral, David, Rumsey, Clare, Intema, Huib, Röttgering, Huub JA, Harwood, Jeremy J, Saunders, Richard, Brüggen, Marcus, Hoeft, Matthias, Stroe, Andra, Weeren, Reinout J van, Sobral, David, Rumsey, Clare, Intema, Huib, Röttgering, Huub JA, Harwood, Jeremy J, Saunders, Richard, Brüggen, Marcus, and Hoeft, Matthias

Abstract

The CIZA J2242.8+5301 cluster hosts an extraordinary, narrow, Mpc-wide, diffuse patch of radio emission tracing travelling shock waves, called a relic. We perform a multi-wavelength of observations of the cluster. We discover radio spectral steepening and increasing spectral curvature in the shock downstream area, indicative of emission produced by spectrally-aged electrons, following a JP ageing model. The curved integrated spectrum towards $16$ GHz challenges the favoured relic formation model. Further, we find a boosting the number density of H$\alpha$ emitters by a factor of $10$, possibly caused by interactions of the galaxies with the shock wave.

Catalog

Books, media, physical & digital resources
See catalog results