Planck intermediate results

X. Physics of the hot gas in the Coma cluster

¹ APC, AstroParticule et Cosmologie, Université Paris Diderot, CNRS/IN2P3, CEA/lrfu, Observatoire de Paris, Sorbonne Paris Cité, 10 rue Alice Domon et Léonie Duquet, 75205 Paris Cedex 13 France
² Aalto University Metsähovi Radio Observatory, Metsähovintie 114, 02540 Kylmälä, Finland
³ Academy of Sciences of Tatarstan, Bauman Str. 20, 420111 Kazan, Republic of Tatarstan, Russia
⁴ Agenzia Spaziale Italiana Science Data Center, c/o ESRIN, via Galileo Galilei, Frascati, Italy
⁵ Agenzia Spaziale Italiana, Viale Liegi 26, Roma, Italy
⁶ Astrophysics Group, Cavendish Laboratory, University of Cambridge, J J Thomson Avenue, Cambridge CB3 0HE, UK
⁷ Atacama Large Millimeter/submillimeter Array, ALMA Santiago Central Offices, Alonso de Cordova 3107, Vitacura, Casilla 763 0355, Santiago, Chile
⁸ CITA, University of Toronto, 60 St. George St., Toronto, ON M5S 3H8, Canada
⁹ CNRS, IRAP, 9 Av. colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France
¹⁰ California Institute of Technology, Pasadena, California, USA
¹¹ Centre of Mathematics for Applications, University of Oslo, Blindern, Oslo, Norway
¹² Centro de Astrofísica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal
¹³ Centro de Estudios de Física del Cosmos de Aragón (CEFCA), Plaza San Juan 1, planta 2, 44001 Teruel, Spain
¹⁴ Computational Cosmology Center, Lawrence Berkeley National Laboratory, Berkeley, California, USA
¹⁵ Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
¹⁶ DSM/Irfu/SPP, CEA-Saclay, 91191 Gif-sur-Yvette Cedex, France
¹⁷ DTU Space, National Space Institute, Technical University of Denmark, Elektrovej 327, 2800 Kgs. Lyngby, Denmark
¹⁸ Département de Physique Théorique, Université de Genève, 24 Quai E. Ansermet, 1211 Genève 4, Switzerland
¹⁹ Departamento de Física Fundamental, Facultad de Ciencias, Universidad de Salamanca, 37008 Salamanca, Spain
²⁰ Departamento de Física, Universidad de Oviedo, Avda. Calvo Sotelo s/n, Oviedo, Spain
²¹ Department of Astronomy and Geodesy, Kazan Federal University, Kremlevskaya Str., 18, 420008 Kazan, Russia
²² Department of Astrophysics/IMAPP, Radboud University Nijmegen, PO Box 9010, 6500 GL Nijmegen, The Netherlands
²³ Department of Physics & Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, British Columbia, Canada
²⁴ Department of Physics and Astronomy, Dana and David Dornsife College of Letter, Arts and Sciences, University of Southern California, Los Angeles, CA 90089, USA
²⁵ Department of Physics and Astronomy, University of Iowa, 203 Van Allen Hall, Iowa City, IA 52242, USA
²⁶ Department of Physics, Gustaf Hällströmin katu 2a, University of Helsinki, Helsinki, Finland
²⁷ Department of Physics, Princeton University, Princeton, New Jersey, USA
²⁸ Department of Physics, University of California, Berkeley, California, USA
²⁹ Department of Physics, University of California, One Shields Avenue, Davis, California, USA
³⁰ Department of Physics, University of California, Santa Barbara, California, USA
³¹ Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois, USA
³² Department of Statistics, Purdue University, 250 N. University Street, West Lafayette, Indiana, USA
³³ Dipartimento di Fisica e Astronomia G. Galilei, Università degli Studi di Padova, via Marzolo 8, 35131 Padova, Italy
³⁴ Dipartimento di Fisica, Università La Sapienza, P.le A. Moro 2, Roma, Italy
³⁵ Dipartimento di Fisica, Università degli Studi di Milano, via Celoria 16, Milano, Italy
³⁶ Dipartimento di Fisica, Università degli Studi di Trieste, via A. Valerio 2, Trieste, Italy
³⁷ Dipartimento di Fisica, Università di Ferrara, via Saragat 1, 44122 Ferrara, Italy
³⁸ Dipartimento di Fisica, Università di Roma Tor Vergata, via della Ricerca Scientifica 1, Roma, Italy
³⁹ Dipartimento di Matematica, Università di Roma Tor Vergata, via della Ricerca Scientifica 1, Roma, Italy
⁴⁰ Discovery Center, Niels Bohr Institute, Blegdamsvej 17, Copenhagen, Denmark
⁴¹ Dpto. Astrofísica, Universidad de La Laguna (ULL), 38206 La Laguna, Tenerife, Spain
⁴² European Southern Observatory, ESO Vitacura, Alonso de Cordova 3107, Vitacura, Casilla 19001, Santiago, Chile
⁴³ European Space Agency, ESAC, Planck Science Office, Camino bajo del Castillo s/n, Urbanización Villafranca del Castillo, Villanueva de la Cañada, Madrid, Spain
⁴⁴ European Space Agency, ESTEC, Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands
⁴⁵ GEPI, Observatoire de Paris, Section de Meudon, 5 place J. Janssen, 92195 Meudon Cedex, France
⁴⁶ Helsinki Institute of Physics, Gustaf Hällströmin katu 2, University of Helsinki, Helsinki, Finland
⁴⁷ INAF – Osservatorio Astrofisico di Catania, via S. Sofia 78, Catania, Italy
⁴⁸ INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35131 Padova, Italy
⁴⁹ INAF – Osservatorio Astronomico di Roma, via di Frascati 33, Monte Porzio Catone, Italy
⁵⁰ INAF – Osservatorio Astronomico di Trieste, via G.B. Tiepolo 11, Trieste, Italy
⁵¹ INAF, Istituto di Radioastronomia, via P. Gobetti 101, 40129 Bologna, Italy
⁵² INAF/IASF Bologna, via Gobetti 101, Bologna, Italy
⁵³ INAF/IASF Milano, via E. Bassini 15, Milano, Italy
⁵⁴ INFN, Sezione di Roma 1, Università di Roma Sapienza, Piazzale Aldo Moro 2, 00185 Roma, Italy
⁵⁵ INRIA, Laboratoire de Recherche en Informatique, Université Paris-Sud 11, Bâtiment 490, 91405 Orsay Cedex, France
⁵⁶ Institut de Planétologie et d’Astrophysique de Grenoble (IPAG), Université Joseph Fourier Grenoble 1/CNRS-INSU, UMR 5274, 38041 Grenoble, France
⁵⁷ ISDC Data Centre for Astrophysics, University of Geneva, ch. d’Ecogia 16, Versoix, Switzerland
⁵⁸ IUCAA, Post Bag 4, Ganeshkhind, Pune University Campus, 411 007 Pune, India
⁵⁹ Imperial College London, Astrophysics group, Blackett Laboratory, PrinceConsort Road, London, SW7 2AZ, UK
⁶⁰ Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125, USA
⁶¹ Institut Néel, CNRS, Université Joseph Fourier Grenoble I, 25 rue des Martyrs, 38041 Grenoble, France
⁶² Institut Universitaire de France, 103 bd Saint-Michel, 75005 Paris, France
⁶³ Institut d’Astrophysique Spatiale, CNRS UMR 8617, Université Paris-Sud 11, Bâtiment 121, Orsay, France
⁶⁴ Institut d’Astrophysique de Paris, CNRS UMR 7095, 98bis boulevard Arago, 75014 Paris, France
⁶⁵ Institute for Space Sciences, Bucharest-Magurale, Romania
⁶⁶ Institute of Astro and Particle Physics, Technikerstrasse 25/8, University of Innsbruck, 6020 Innsbruck, Austria
⁶⁷ Institute of Astronomy and Astrophysics, Academia Sinica, Taipei, Taiwan
⁶⁸ Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
⁶⁹ Institute of Theoretical Astrophysics, University of Oslo, Blindern, Oslo, Norway
⁷⁰ Instituto de Astrofísica de Canarias, C/Vía Láctea s/n, La Laguna, Tenerife, Spain
⁷¹ Instituto de Física de Cantabria (CSIC-Universidad de Cantabria), Avda. de los Castros s/n, Santander, Spain
⁷² Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California, USA
⁷³ Jodrell Bank Centre for Astrophysics, Alan Turing Building, School of Physics and Astronomy, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK
⁷⁴ Kapteyn Astronomical Institute, University of Groningen, Landleven 12, 9747 AD Groningen, The Netherlands
⁷⁵ Kavli Institute for Cosmology Cambridge, Madingley Road, Cambridge, CB3 0HA, UK
⁷⁶ LAL, Université Paris-Sud, CNRS/IN2P3, Orsay, France
⁷⁷ LERMA, CNRS, Observatoire de Paris, 61 avenue de l’Observatoire, Paris, France
⁷⁸ Laboratoire AIM, IRFU/Service d’Astrophysique – CEA/DSM – CNRS – Université Paris Diderot, Bât. 709, CEA-Saclay, 91191 Gif-sur-Yvette Cedex, France
⁷⁹ Laboratoire Traitement et Communication de l’Information, CNRS UMR 5141 and Télécom ParisTech, 46 rue Barrault, 75634 Paris Cedex 13, France
⁸⁰ Laboratoire de Physique Subatomique et de Cosmologie, Université Joseph Fourier Grenoble I, CNRS/IN2P3, Institut National Polytechnique de Grenoble, 53 rue des Martyrs, 38026 Grenoble Cedex, France
⁸¹ Laboratoire de Physique Théorique, Université Paris-Sud 11 & CNRS, Bâtiment 210, 91405 Orsay, France
⁸² Lawrence Berkeley National Laboratory, Berkeley, California, USA
⁸³ Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85741 Garching, Germany
⁸⁴ Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstraße, 85748 Garching, Germany
⁸⁵ MilliLab, VTT Technical Research Centre of Finland, Tietotie 3, Espoo, Finland
⁸⁶ Minnesota Institute for Astrophysics, School of Physics and Astronomy, University of Minnesota, 116 Church St. SE, Minneapolis, MN 55455, USA
⁸⁷ National University of Ireland, Department of Experimental Physics, Maynooth, Co. Kildare, Ireland
⁸⁸ Niels Bohr Institute, Blegdamsvej 17, Copenhagen, Denmark
⁸⁹ Observational Cosmology, Mail Stop 367-17, California Institute of Technology, Pasadena, CA, 91125, USA
⁹⁰ Optical Science Laboratory, University College London, Gower Street, London, UK
⁹¹ SISSA, Astrophysics Sector, via Bonomea 265, 34136, Trieste, Italy
⁹² School of Physics and Astronomy, Cardiff University, Queens Buildings, The Parade, Cardiff, CF24 3AA, UK
⁹³ Space Research Institute (IKI), Profsoyuznaya 84/32, Moscow, Russia
⁹⁴ Space Research Institute (IKI), Russian Academy of Sciences, Profsoyuznaya Str. 84/32, 117997 Moscow, Russia
⁹⁵ Space Sciences Laboratory, University of California, Berkeley, California, USA
⁹⁶ Stanford University, Dept of Physics, Varian Physics Bldg, 382 via Pueblo Mall, Stanford, California, USA
⁹⁷ TÜBİTAK National Observatory, Akdeniz University Campus, 07058 Antalya, Turkey
⁹⁸ UPMC Univ. Paris 6, UMR7095, 98bis boulevard Arago, 75014 Paris, France
⁹⁹ Universität Heidelberg, Institut für Theoretische Astrophysik, Albert-Überle-Str. 2, 69120 Heidelberg, Germany
¹⁰⁰ Université Denis Diderot Paris 7, 75205 Paris Cedex 13, France
¹⁰¹ Université de Toulouse, UPS-OMP, IRAP, 31028 Toulouse Cedex 4, France
¹⁰² University Observatory, Ludwig Maximilian University of Munich, Scheinerstrasse 1, 81679 Munich, Germany
¹⁰³ University of Granada, Departamento de Física Teórica y delCosmos, Facultad de Ciencias, Granada, Spain
¹⁰⁴ University of Miami, Knight Physics Building, 1320 Campo Sano Dr., Coral Gables, Florida, USA
¹⁰⁵ Warsaw University Observatory, Aleje Ujazdowskie 4, 00-478 Warszawa, Poland

Received: 17 August 2012
Accepted: 26 November 2012

Abstract

We present an analysis of Planck satellite data on the Coma cluster observed via the Sunyaev-Zeldovich effect. Thanks to its great sensitivity, Planck is able, for the first time, to detect SZ emission up to r ≈ 3 × R₅₀₀. We test previously proposed spherically symmetric models for the pressure distribution in clusters against the azimuthally averaged data. In particular, we find that the Arnaud et al. (2010, A&A, 517, A92) “universal” pressure profile does not fit Coma, and that their pressure profile for merging systems provides a reasonable fit to the data only at r < R₅₀₀; by r = 2 × R₅₀₀ it underestimates the observed y profile by a factor of ≃2. This may indicate that at these larger radii either: i) the cluster SZ emission is contaminated by unresolved SZ sources along the line of sight; or ii) the pressure profile of Coma is higher at r > R₅₀₀ than the mean pressure profile predicted by the simulations used to constrain the models. The Planck image shows significant local steepening of the y profile in two regions about half a degree to the west and to the south-east of the cluster centre. These features are consistent with the presence of shock fronts at these radii, and indeed the western feature was previously noticed in the ROSAT PSPC mosaic as well as in the radio. Using Plancky profiles extracted from corresponding sectors we find pressure jumps of 4.9_-0.2^+0.4 and 5.0_-0.1^+1.3 in the west and south-east, respectively. Assuming Rankine-Hugoniot pressure jump conditions, we deduce that the shock waves should propagate with Mach number M_w = 2.03_-0.04^+0.09 and M_se = 2.05_-0.02^+0.25 in the west and south-east, respectively. Finally, we find that the y and radio-synchrotron signals are quasi-linearly correlated on Mpc scales, with small intrinsic scatter. This implies either that the energy density of cosmic-ray electrons is relatively constant throughout the cluster, or that the magnetic fields fall off much more slowly with radius than previously thought.