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12 results on '"Radio lines: General"'

1. The degeneracy between primordial non-Gaussianity and foregrounds in 21cm intensity mapping experiments

Author

Alkistis Pourtsidou, Stefano Camera, and Steven Cunnington

Subjects
Cosmology and Nongalactic Astrophysics (astro-ph.CO), Large-scale structure of Universe, Radio lines: general, FOS: Physical sciences, Astrophysics, 01 natural sciences, symbols.namesake, Non-Gaussianity, 0103 physical sciences, Nuisance parameter, Planck, 010303 astronomy & astrophysics, Physics, 010308 nuclear & particles physics, Cosmology: observations, Intensity mapping, Order (ring theory), Spectral density, Astronomy and Astrophysics, Galaxy, Cosmology: theory, Space and Planetary Science, symbols, Degeneracy (mathematics), Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

Potential evidence for primordial non-Gaussianity (PNG) is expected to lie in the largest scales mapped by cosmological surveys. Forthcoming 21cm intensity mapping experiments will aim to probe these scales by surveying neutral hydrogen (HI) within galaxies. However, foreground signals dominate the faint 21cm emission, meaning foreground cleaning is required to recover the cosmological signal. The effect this has is to damp the HI power spectrum on the largest scales, especially along the line-of-sight. Whilst there is agreement that this contamination is potentially problematic for probing PNG, it is yet to be fully explored and quantified. In this work we carry out the first forecasts on $f_\text{NL}$ that incorporate simulated foreground maps that are removed using techniques employed in real data. Using an MCMC analysis, we demonstrate that foreground cleaned data recovers hugely biased values ($f_\text{NL} = -102.1_{-7.96}^{+8.39}$ [68% CL]) on our $f_\text{NL}=0$ fiducial input. Introducing a model with fixed parameters for the foreground contamination allows us to recover unbiased results ($f_\text{NL} = -2.94_{-11.9}^{+11.4}$). However, it is not clear that we will have sufficient understanding of foreground contamination to allow for such rigid models. Treating the main parameter $k_\parallel^\text{FG}$ in our foreground model as a nuisance parameter and marginalizing over it, still recovers unbiased results but at the expense of much larger errors ($f_\text{NL} = 0.75^{+40.2}_{-44.5}$), that can only be reduced by imposing the Planck 2018 prior. Our results show that significant progress on understanding and controlling foreground removal effects is necessary in order to study PNG with HI intensity mapping., Comment: 15 pages, 8 figures. The busy reader should study Fig 8 which demonstrates the degeneracy between f_NL and k_FG the main parameter in our model to account for foreground removal effects. Accepted by MNRAS

Published
2020
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2. Parametrizations of the 21-cm global signal and parameter estimation from single-dipole experiments

Author

Jack O. Burns, Geraint Harker, Jordan Mirocha, Jonathan R. Pritchard, Imperial College Trust, Science and Technology Facilities Council (STFC), Commission of the European Communities, and Science and Technology Facilities Council [2006-2012]

Subjects
DARK-AGES, MODELS, Astronomy & Astrophysics, 01 natural sciences, Signal, cosmology: theory, 0103 physical sciences, dark ages, reionization, first stars, Statistical physics, 010303 astronomy & astrophysics, Reionization, Physics, methods: statistical, Science & Technology, 010308 nuclear & particles physics, Estimation theory, Hyperbolic function, COSMIC DAWN, Astronomy and Astrophysics, Dark Ages Radio Explorer, diffuse radiation, Maxima and minima, 0201 Astronomical And Space Sciences, Space and Planetary Science, COSMOLOGY, Physical Sciences, astro-ph.CO, Radio frequency, radio lines: general, Parametrization
Abstract

One approach to extracting the global 21-cm signal from total-power measurements at low radio frequencies is to parametrize the different contributions to the data and then fit for these parameters. We examine parametrizations of the 21-cm signal itself, and propose one based on modelling the Ly α background, intergalactic medium temperature and hydrogen ionized fraction using tanh functions. This captures the shape of the signal from a physical modelling code better than an earlier parametrization based on interpolating between maxima and minima of the signal, and imposes a greater level of physical plausibility. This allows less biased constraints on the turning points of the signal, even though these are not explicitly fit for. Biases can also be alleviated by discarding information which is less robustly described by the parametrization, for example by ignoring detailed shape information coming from the covariances between turning points or from the high-frequency parts of the signal, or by marginalizing over the high-frequency parts of the signal by fitting a more complex foreground model. The fits are sufficiently accurate to be usable for experiments gathering 1000 h of data, though in this case it may be important to choose observing windows which do not include the brightest areas of the foregrounds. Our assumption of pointed, single-antenna observations and very broad-band fitting makes these results particularly applicable to experiments such as the Dark Ages Radio Explorer, which would study the global 21-cm signal from the clean environment of a low lunar orbit, taking data from the far side.

Published
2015
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3. FOREST unbiased Galactic plane imaging survey with the Nobeyama 45 m telescope (FUGIN). I. Project overview and initial results

Author

Satoshi Yoshiike, Hiroyuki Nakanishi, Hiroko Shinnaga, Kazuki Tokuda, Masumichi Seta, Tetsuhiro Minamidani, Jean Costes, Mika Kuriki, Masato Tsuboi, Mikito Kohno, Yusuke Hattori, Nagito Koide, Yumiko Oasa, Hidetoshi Sano, Yuya Tsuda, Toshihiro Omodaka, Tsuyoshi Inoue, Erik Muller, Toshikazu Onishi, Atsushi Nishimura, Akihiko Hirota, Takeaki Ozawa, Kazuhisa Kamegai, Mitsuhiro Matsuo, James O. Chibueze, Norikazu Mizuno, Sho Kuwahara, Toshihiro Handa, Kengo Tachihara, Ryo Takahashi, Mareki Honma, Shinji Fujita, Kana Morokuma-Matsui, Mitsuyoshi Yamagishi, Nario Kuno, Yukinori Kobayashi, Kazufumi Torii, Satoshi Ohashi, Tomofumi Umemoto, Tomoka Tosaki, Sachiko Onodera, Yoshiaki Sofue, Aya E. Higuchi, and Naoko Matsumoto

Subjects
FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, ISM: clouds, 01 natural sciences, law.invention, Quadrant (plane geometry), Telescope, surveys, law, 0103 physical sciences, Angular resolution, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Physics, Spiral galaxy, 010308 nuclear & particles physics, Molecular cloud, Astronomy, Astronomy and Astrophysics, Galactic plane, Astrophysics - Astrophysics of Galaxies, ISM: molecules, Galaxy, Interstellar medium, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), radio lines: general, Galaxy: kinematics and dynamics
Abstract

著者人数: 44名, Accepted: 2017-06-15, 資料番号: SA1170167000

Published
2017
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4. The Atacama Compact Array (ACA)

Author

Shigehisa Takakuwa, Seiichi Sakamoto, Masao Saito, Junji Inatani, Ryohei Kawabe, Daisuke Iono, Ryusuke Ogasawara, Baltasar Vila Vilaro, Sachiko K. Okumura, Tetsuo Hasegawa, Koh-Ichiro Morita, Ken'ichi Tatematsu, Masahiro Sugimoto, George Kosugi, Takeshi Kamazaki, Masato Ishiguro, Satoru Iguchi, and Hitoshi Kiuchi

Subjects
Physics, Brightness, business.industry, Wavelength range, radio continuum: general, techniques: image processing, Astronomy and Astrophysics, Submillimeter Array, symbols.namesake, Optics, Fourier transform, techniques: interferometric, Space and Planetary Science, Homogeneous, symbols, Low spatial frequency, Millimeter, Spatial frequency, instrumentation: interferometers, radio lines: general, business
Abstract

For realizing high fidelity of imaging with mosaicing observations, the Atacama Large Millimeter/submillimeter Array (ALMA) consists of a homogeneous array of 12 m antennas (12 m Array) and the Atacama Compact Array (ACA) in order to cover all spatial frequency Fourier components of the brightness distribution of observed sources. The array is located at an altitude site of about 5000 m with an operating wavelength range of 0.3 to 3 mm. ACA is an array composed of four 12 m dishes [TP (Total Power) Array] and twelve 7 m dishes (7 m Array). The 7 m Array has a very compact configuration to take short-baseline data corresponding to the low spatial frequency Fourier components. The 7 m Array has two configurations extended over 30–50 m to avoid shadowing at low elevation. The scientific importances and operation concepts of ACA, and the system design of ACA and its performance are presented in this paper.

Published
2009
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5. On the detectability of intelligent civilizations in the galaxy

Author

Les W. Field and N. Djuric

Subjects
Physics, Value (ethics), lcsh:Astronomy, astrobiology, Optical communication, Extraterrestrial intelligence, Astronomy, Astronomy and Astrophysics, Astrophysics, galaxy: stellar content, extraterrestrial intelligence, Galaxy, lcsh:QB1-991, Stars, Broadband, Limit (mathematics), radio lines: general, Event (probability theory)
Abstract

In this paper we argue for the possibility that even in the event of a Galaxy teeming with extraterrestrial intelligence (ETI) the probability of receiving recognizable signals from the ETIs may be very low. There are two majors factors that may limit our ability to detect other civilizations. (i) Evolutionary mismatches may cause difficulties analogous to humans attempting to communicate with lower primates. (ii) Independent evolutionary paths resulting from differing planetary/stellar environments may result in life whose cognitive processes and consequent perceptions of the universe are very different from ours. Interpreting signals from such civilizations may prove a very difficult or even futile task. Even on Earth, an example of a cognitive mismatch is that between humans and dolphins, where evolution in very different environments has led to difficulty in establishing communication between these two species. The main effect of the second factor is to limit communication while the effect of the first is to constrain what communication is possible to a "window of opportunity", a finite period of time, ??, when communication may be possible before diverging evolution makes it impossible. For example, if the number of ETIs in the Galaxy is one million and if ?? < 10 6 years, the average separation of "contactable" civilizations, (r) > 5 ? 10 3 light years so that one star in 10 10 harbors such a civilization. If the above arguments are correct we reach the following conclusions. The absence of detected signals does not translate into an absence of ETI?s. Targeting individual stars in the search for ETI has a low probability of success. The use of radio signals is of limited value because with such large separations between "contactable" civilizations interstellar scintillation strongly limits the propagation of radio signals. Similarly, optical communication would be hindered by interstellar extinction. Possible alternatives to current searches for narrow band signals include listening for modulated broadband signals searching for narrow-band signals in the microwave/FIR spectrum and searching for evidence of artificially processed environments. All such searches would need to be "all sky" to have a reasonable chance of success.

Published
2003
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6. 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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7. THE ALMA SPECTROSCOPIC SURVEY IN THE HUBBLE ULTRA DEEP FIELD: IMPLICATIONS FOR SPECTRAL LINE INTENSITY MAPPING AT MILLIMETER WAVELENGTHS AND CMB SPECTRAL DISTORTIONS

Author

Roberto Decarli, Paulo C. Cortes, Fabian Walter, Jeff Wagg, Frank Bertoldi, Jens Chluba, Axel Weiss, Manuel Aravena, Jacqueline Hodge, Chris Carilli, Gergö Popping, Dominik Riechers, Carilli, Christopher [0000-0001-6647-3861], and Apollo - University of Cambridge Repository

Subjects
Brightness, molecular data, Astrophysics::High Energy Astrophysical Phenomena, Cosmic microwave background, FOS: Physical sciences, cosmic background radiation, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, 01 natural sciences, Spectral line, Sky brightness, 0103 physical sciences, galaxies: formation, Surface brightness, dark ages, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Physics, 010308 nuclear & particles physics, Intensity mapping, Astronomy and Astrophysics, Hubble Ultra-Deep Field, Astrophysics - Astrophysics of Galaxies, Redshift, reionization, first stars, techniques: imaging spectroscopy, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), radio lines: general
Abstract

We present direct estimates of the mean sky brightness temperature in observing bands around 99GHz and 242GHz due to line emission from distant galaxies. These values are calculated from the summed line emission observed in a blind, deep survey for specrtal line emission from high redshift galaxies using ALMA (the 'ASPECS' survey). In the 99 GHz band, the mean brightness will be dominated by rotational transitions of CO from intermediate and high redshift galaxies. In the 242GHz band, the emission could be a combination of higher order CO lines, and possibly [CII] 158$\mu$m line emission from very high redshift galaxies ($z \sim 6$ to 7). The mean line surface brightness is a quantity that is relevant to measurements of spectral distortions of the cosmic microwave background, and as a potential tool for studying large-scale structures in the early Universe using intensity mapping. While the cosmic volume and the number of detections are admittedly small, this pilot survey provides a direct measure of the mean line surface brightness, independent of conversion factors, excitation, or other galaxy formation model assumptions. The mean surface brightness in the 99GHZ band is: $T_B = 0.94\pm 0.09$ $\mu$K. In the 242GHz band, the mean brightness is: $T_B = 0.55\pm 0.033$ $\mu$K. These should be interpreted as lower limits on the average sky signal, since we only include lines detected individually in the blind survey, while in a low resolution intensity mapping experiment, there will also be the summed contribution from lower luminosity galaxies that cannot be detected individually in the current blind survey., Comment: To appear the Astrophysical Journal, incorporating the first and second round of referee comments. Revised version 2 fixed typo in brightness units, equation, and text, and revised acknowledgements

Published
2016
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8. The Hitachi and Takahagi 32 m radio telescopes: Upgrade of the antennas from satellite communication to radio astronomy

Author

Soon, Kang Lou, Ohyama, Tomoaki, Kono, Yusuke, Yonekura, Yoshinori, Saito, Yu, Sugiyama, Koichiro, Momose, Munetake, Yokosawa, Masayoshi, Ogawa, Hideo, Kimura, Kimihiro, Abe, Yasuhiro, Nishimura, Atsushi, Hasegawa, Yutaka, Fujisawa, Kenta, Miyamoto, Yusuke, Sawada-Satoh, Satoko, Kobayashi, Hideyuki, Kawaguchi, Noriyuki, Honma, Mareki, Shibata, Katsunori M., Sato, Katsuhisa, Ueno, Yuji, Jike, Takaaki, Tamura, Yoshiaki, Hirota, Tomoya, Miyazaki, Atsushi, Niinuma, Kotaro, Sorai, Kazuo, Takaba, Hiroshi, Hachisuka, Kazuya, Kondo, Tetsuro, Sekido, Mamoru, Murata, Yasuhiro, Nakai, Naomasa, and Omodaka, Toshihiro

Subjects
Physics, instrumentation: detectors, radio continuum: general, Astronomy, 020206 networking & telecommunications, Astronomy and Astrophysics, 02 engineering and technology, 01 natural sciences, law.invention, Radio telescope, Upgrade, masers, Space and Planetary Science, law, 0103 physical sciences, Very-long-baseline interferometry, 0202 electrical engineering, electronic engineering, information engineering, Communications satellite, Maser, instrumentation: interferometers, radio lines: general, 010303 astronomy & astrophysics, Radio astronomy
Abstract

著者人数: 35名, Accepted: 2016-04-04, 資料番号: SA1160183000

Published
2016
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9. Non-parametric foreground subtraction for 21cm epoch of reionization experiments

Author

Michiel A. Brentjens, Geraint Harker, Vibor Jelić, Sarod Yatawatta, Gianni Bernardi, Garrelt Mellema, Vishambhar Pandey, Saleem Zaroubi, Rajat M. Thomas, Léon V. E. Koopmans, Panagiotis Labropoulos, Benedetta Ciardi, A. G. de Bruyn, Joop Schaye, A. R. Offringa, and Kapteyn Astronomical Institute

Subjects
21 CENTIMETER FLUCTUATIONS, Cosmology and Nongalactic Astrophysics (astro-ph.CO), MODELS, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Synthetic data, Smoothing spline, SIGNALS, cosmology: theory, TOMOGRAPHY, MAPS, methods: statistical, diffuse radiation, radio lines: general, Reionization, Parametric statistics, Physics, Nonparametric statistics, CONSTRAINTS, Astronomy and Astrophysics, LOFAR, Redshift, SIMULATIONS, Space and Planetary Science, HIGH REDSHIFTS, EMISSION, Algorithm, Smoothing, Astrophysics - Cosmology and Nongalactic Astrophysics, COSMIC REIONIZATION
Abstract

An obstacle to the detection of redshifted 21cm emission from the epoch of reionization (EoR) is the presence of foregrounds which exceed the cosmological signal in intensity by orders of magnitude. We argue that in principle it would be better to fit the foregrounds non-parametrically - allowing the data to determine their shape - rather than selecting some functional form in advance and then fitting its parameters. Non-parametric fits often suffer from other problems, however. We discuss these before suggesting a non-parametric method, Wp smoothing, which seems to avoid some of them. After outlining the principles of Wp smoothing we describe an algorithm used to implement it. We then apply Wp smoothing to a synthetic data cube for the LOFAR EoR experiment. The performance of Wp smoothing, measured by the extent to which it is able to recover the variance of the cosmological signal and to which it avoids leakage of power from the foregrounds, is compared to that of a parametric fit, and to another non-parametric method (smoothing splines). We find that Wp smoothing is superior to smoothing splines for our application, and is competitive with parametric methods even though in the latter case we may choose the functional form of the fit with advance knowledge of the simulated foregrounds. Finally, we discuss how the quality of the fit is affected by the frequency resolution and range, by the characteristics of the cosmological signal and by edge effects., Comment: 15 pages, 12 figures; lengthened and two figures added, to match version accepted by MNRAS

Published
2009
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10. Foreground simulations for the LOFAR - Epoch of Reionization Experiment

Author

Panagiotis Labropoulos, Vishambhar Pandey, Michiel A. Brentjens, Léon V. E. Koopmans, Sarod Yatawatta, Ger de Bruyn, Benedetta Ciardi, Vibor Jelić, Gianni Bernardi, Joop Schaye, Saleem Zaroubi, Rajat M. Thomas, Geraint Harker, Astronomy, and Kapteyn Astronomical Institute

Subjects
RADIO-SOURCES, radio lines : general, 21 CENTIMETER FLUCTUATIONS, radio continuum : general, media_common.quotation_subject, instrumentation: interferometers, cosmology: observation, cosmology: theory, diffuse radiation, radio continuum: general, radio lines: general, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, PRE-REIONIZATION, Precision Array for Probing the Epoch of Reionization, law.invention, GALAXY REDSHIFT SURVEY, law, cosmology : observation, instrumentation : interferometers, Faraday cage, Reionization, media_common, Polynomial regression, Physics, LINEAR-POLARIZATION, Line-of-sight, Astrophysics (astro-ph), Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, LOFAR, SPIN TEMPERATURE, Redshift, cosmology : theory, NEUTRAL HYDROGEN, GALACTIC EMISSION, Space and Planetary Science, Sky, PROBE WMAP OBSERVATIONS, INTERGALACTIC MEDIUM
Abstract

Future high redshift 21-cm experiments will suffer from a high degree of contamination, due both to astrophysical foregrounds and to non-astrophysical and instrumental effects. In order to reliably extract the cosmological signal from the observed data, it is essential to understand very well all data components and their influence on the extracted signal. Here we present simulated astrophysical foregrounds datacubes and discuss their possible statistical effects on the data. The foreground maps are produced assuming 5 deg x 5 deg windows that match those expected to be observed by the LOFAR Epoch-of-Reionization (EoR) key science project. We show that with the expected LOFAR-EoR sky and receiver noise levels, which amount to ~52 mK at 150 MHz after 300 hours of total observing time, a simple polynomial fit allows a statistical reconstruction of the signal. We also show that the polynomial fitting will work for maps with realistic yet idealised instrument response, i.e., a response that includes only a uniform uv coverage as a function of frequency and ignores many other uncertainties. Polarized galactic synchrotron maps that include internal polarization and a number of Faraday screens along the line of sight are also simulated. The importance of these stems from the fact that the LOFAR instrument, in common with all current interferometric EoR experiments has an instrumentally polarized response., Comment: 18 figures, 3 tables, accepted to be published in MNRAS

Published
2008
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11. HIFI observations of water in the atmosphere of comet C/2008 Q3 (Garradd)

Author

L. M. Lara, Miriam Rengel, T. Klein, Nicolas Biver, M. R. Kidger, R. Moreno, Emmanuel Jehin, E. Lellouch, Michael Küppers, C. Kasemann, David A. Naylor, C. Waelkens, Pieter Dieleman, T. de Graauw, Dominique Bockelée-Morvan, Michael Olberg, E. A. Bergin, Pieter R. Roelfsema, M. Caris, Jean Manfroid, M. I. Blecka, T. Encrenaz, M. de Val-Borro, L. Decin, J. Crovisier, Slawomira Szutowicz, Christopher Jarchow, Bart Vandenbussche, José Cernicharo, J. A. D. L. Blommaert, Damien Hutsemekers, N. Thomas, Geoffrey A. Blake, Rolf Guesten, Paul Hartogh, Alexander S. Medvedev, Marek Banaszkiewicz, Arnold O. Benz, Rudolf Schieder, P. J. Encrenaz, F. Bensch, B. M. Swinyard, Dariusz C. Lis, Thibault Cavalié, Martin Emprechtinger, Max-Planck-Institut für Sonnensystemforschung = Max Planck Institute for Solar System Research (MPS), Max-Planck-Gesellschaft, 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), California Institute of Technology (CALTECH), Space Research Centre of Polish Academy of Sciences (CBK), Polska Akademia Nauk = Polish Academy of Sciences (PAN), Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Sciences et Technologies - Bordeaux 1 (UB), Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux (L3AB), European Southern Observatory (ESO), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University-Smithsonian Institution, Laboratoire Optimisation de la Conception et Ingénierie de l'Environnement (LOCIE), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), Centro de Investigaciones Biológicas (CSIC), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Instituut voor Sterrenkunde [Leuven], Catholic University of Leuven - Katholieke Universiteit Leuven (KU Leuven), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-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 de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Centre National de la Recherche Scientifique (CNRS), Centre Alexis Vautrin (CAV), Max-Planck-Institut für Radioastronomie (MPIFR), Onsala Space Observatory, Chalmers University of Technology [Göteborg], Astronomy, Max Planck Institute for Solar System Research (MPS), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Sciences et Technologies - Bordeaux 1, Smithsonian Institution-Harvard University [Cambridge], and École normale supérieure - Paris (ENS Paris)

Subjects
ROTATIONAL-EXCITATION, Electron density, 010504 meteorology & atmospheric sciences, Mean kinetic temperature, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Infrared, Comet, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], FOS: Physical sciences, Astrophysics, 01 natural sciences, RADIATIVE-TRANSFER, 0103 physical sciences, Radiation trapping, Spectroscopy, 010303 astronomy & astrophysics, SATELLITE, 0105 earth and related environmental sciences, Line (formation), Earth and Planetary Astrophysics (astro-ph.EP), Physics, LEE, submillimeter: general, Astronomy and Astrophysics, MODEL, 13. Climate action, Space and Planetary Science, comets: individual: C/2008 Q3, ODIN, VAPOR, radio lines: general, techniques: spectroscopic, Excitation, Astrophysics - Earth and Planetary Astrophysics
Abstract

High-resolution far-infrared and sub-millimetre spectroscopy of water lines is an important tool to understand the physical and chemical properties of cometary atmospheres. We present observations of several rotational ortho- and para-water transitions in comet C/2008 Q3 (Garradd) performed with HIFI on Herschel. These observations have provided the first detection of the 2_{12}-1_{01} (1669 GHz) ortho and 1_{11}-0_{00} (1113 GHz) para transitions of water in a cometary spectrum. In addition, the ground-state transition 1_{10}-1_{01} at 557 GHz is detected and mapped. By detecting several water lines quasi-simultaneously and mapping their emission we can constrain the excitation parameters in the coma. Synthetic line profiles are computed using excitation models which include excitation by collisions, solar infrared radiation, and radiation trapping. We obtain the gas kinetic temperature, constrain the electron density profile, and estimate the coma expansion velocity by analyzing the map and line shapes. We derive water production rates of 1.7-2.8 x 10^{28} s^{-1} over the range r_h = 1.83-1.85 AU., Comment: 7 figures, v2: minor changes, updated version of arXiv:1005.2969v1. Accepted for publication in Astronomy and Astrophysics, Herschel special issue on Herschel First Science Results

Published
2010
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12. The earliest phases of high-mass star formation: the NGC 6334-NGC 6357 complex

Author

Andrew Walsh, D. Russeil, Frédérique Motte, Sylvain Bontemps, Nicola Schneider, Annie Zavagno, Laboratoire d'Astrophysique de Marseille (LAM), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Observatoire Astronomique de Marseille Provence (OAMP), Université de Provence - Aix-Marseille 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), 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), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Sciences et Technologies - Bordeaux 1 (UB), Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux (L3AB), Laboratoire de Probabilités et Modèles Aléatoires (LPMA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Centre National d'Études Spatiales [Toulouse] (CNES), 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), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Sciences et Technologies - Bordeaux 1, and Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université Pierre et Marie Curie - Paris 6 (UPMC)

Subjects
010504 meteorology & atmospheric sciences, Stellar mass, Infrared, Astrophysics, 01 natural sciences, law.invention, Telescope, law, 0103 physical sciences, regions, Protostar, Basso continuo, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Physics, stars: formation, extinction, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Star formation, Molecular cloud, Astronomy, Astronomy and Astrophysics, [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Stars, H ii, radio continuum: ISM, Space and Planetary Science, submillimeter: ISM, dust, radio lines: general
Abstract

International audience; Context. Our knowledge of high-mass star formation has been mainly based on follow-up studies of bright sources found by IRAS, and has thus been incomplete for its earliest phases, which are inconspicuous at infrared wavelengths. With a new generation of powerful bolometer arrays, unbiased large-scale surveys of nearby high-mass star-forming complexes now search for the high-mass analog of low-mass cores and class 0 protostars. Aims: Following the pioneering study of Cygnus X, we investigate the star-forming region NGC 6334-NGC 6357 (~1.7 kpc). Methods: We study the complex NGC 6334-NGC 6357 in an homogeneous way following the previous work of Motte and collaborators. We used the same method to extract the densest cores which are the most likely sites for high-mass star formation. We analyzed the SIMBA/SEST 1.2 mm data presented in Munoz and coworkers, which covers all high-column density areas (A v ≥ 15 mag) of the NGC 6334-NGC 6357 complex and extracted dense cores following the method used for Cygnus X. We constrain the properties of the most massive dense cores (M > 100 M_ȯ) using new molecular line observations (as SiO, N2H+,H13CO+, HCO+ (1-0) and CH3CN) with Mopra and a complete cross-correlation with infrared databases (MSX, GLIMPSE, MIPSGAL) and literature. Results: We extracted 163 massive dense cores of which 16 are more massive than 200 M_ȯ. These high-mass dense cores have a typical FWHM size of 0.37 pc, an average mass of M ~ 600 M_ȯ, and a volume-averaged density of ~ 1.5 × 105 cm-3. Among these massive dense cores, 6 are good candidates for hosting high-mass infrared-quiet protostars, 9 cores are classified as high-luminosity infrared protostars, and we find only one high-mass starless clump (~0.3 pc, ~ 4 × 104 cm-3) that is gravitationally bound. Conclusions: Since our sample is derived from a single molecular complex and covers every embedded phase of high-mass star formation, it provides a statistical estimate of the lifetime of massive stars. In contrast to what is found for low-mass class 0 and class I phases, the infrared-quiet protostellar phase of high-mass stars may last as long as their more well known high-luminosity infrared phase. As in Cygnus X, the statistical lifetime of high-mass protostars is shorter than found for nearby, low-mass star-forming regions which implies that high-mass pre-stellar and protostellar cores are in a dynamic state, as expected in a molecular cloud where turbulent and/or dynamical processes dominate. Based on observations made with Mopra telescope. The Mopra telescope is part of the Australia Telescope which is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO.Table 1 and Appendix are only available in electronic form at http://www.aanda.orgProfiles as FITS files are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/515/A55

Published
2010
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