Issue |
A&A
Volume 502, Number 2, August I 2009
|
|
---|---|---|
Page(s) | 437 - 443 | |
Section | Cosmology (including clusters of galaxies) | |
DOI | https://doi.org/10.1051/0004-6361/200912086 | |
Published online | 04 June 2009 |
Constraints on the multi-TeV particle population in the Coma galaxy cluster with HESS observations
1
Max-Planck-Institut für Kernphysik, PO Box 103980, 69029 Heidelberg, Germany
2
Dublin Institute for Advanced Studies, 5 Merrion Square, Dublin 2, Ireland
3
Yerevan Physics Institute, 2 Alikhanian Brothers St., 375036 Yerevan, Armenia
4
Universität Erlangen-Nürnberg, Physikalisches Institut, Erwin-Rommel-Str. 1, 91058 Erlangen, Germany
5
University of Durham, Department of Physics, South Road, Durham DH1 3LE, UK
6
Centre d'Étude Spatiale des Rayonnements, CNRS/UPS, 9 Av. du Colonel Roche, BP 4346, 31029 Toulouse Cedex 4, France
7
Astroparticule et Cosmologie (APC), CNRS, Université Paris 7 Denis Diderot, 10, rue Alice Domon et Leonie Duquet, 75205 Paris Cedex 13; (UMR 7164 (CNRS, Université Paris VII, CEA, Observatoire de Paris)) , France
8
Landessternwarte, Universität Heidelberg, Königstuhl, 69117 Heidelberg, Germany
9
Institut für Physik, Humboldt-Universität zu Berlin, Newtonstr. 15, 12489 Berlin, Germany
10
LUTH, Observatoire de Paris, CNRS, Université Paris Diderot, 5 Place Jules Janssen, 92190 Meudon, France
11
IRFU/DSM/CEA, CE Saclay, 91191 Gif-sur-Yvette, Cedex, France
12
Nicolaus Copernicus Astronomical Center, ul. Bartycka 18, 00-716 Warsaw, Poland
13
Unit for Space Physics, North-West University, Potchefstroom 2520, South Africa
14
Laboratoire d'Astrophysique de Grenoble, INSU/CNRS, Université Joseph Fourier, BP 53, 38041 Grenoble Cedex 9, France
15
LPNHE, Université Pierre et Marie Curie Paris 6, Université Denis Diderot Paris 7, CNRS/IN2P3, 4 Place Jussieu, 75252 Paris Cedex 5, France
16
Laboratoire Leprince-Ringuet, École Polytechnique, CNRS/IN2P3, 91128 Palaiseau, France
17
Laboratoire d'Annecy-le-Vieux de Physique des Particules, CNRS/IN2P3, 9 Chemin de Bellevue, BP 110, 74941 Annecy-le-Vieux Cedex, France
18
University of Namibia, Private Bag 13301, Windhoek, Namibia
19
Instytut Fizyki Jądrowej PAN, ul. Radzikowskiego 152, 31-342 Kraków, Poland
20
Laboratoire de Physique Théorique et Astroparticules, Université Montpellier 2, CNRS/IN2P3, CC 70, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France
21
Universität Hamburg, Institut für Experimentalphysik, Luruper Chaussee 149, 22761 Hamburg, Germany
22
School of Physics & Astronomy, University of Leeds, Leeds LS2 9JT, UK
23
Institut für Astronomie und Astrophysik, Universität Tübingen, Sand 1, 72076 Tübingen, Germany
24
Department of Physics, Kyoto University, Oiwake-cho, Kitashirakawa, Sakyo-ku, Kyoto 606-8502, Japan
25
Toruń Centre for Astronomy, Nicolaus Copernicus University, ul. Gagarina 11, 87-100 Toruń, Poland
26
Charles University, Faculty of Mathematics and Physics, Institute of Particle and Nuclear Physics, V Holešovičkách 2, 180 00 Prague, Czech Republic
27
European Associated Laboratory for Gamma-Ray Astronomy, jointly supported by CNRS and MPG
28
Obserwatorium Astronomiczne, Uniwersytet Jagielloński, ul. Orla 171, 30-244 Kraków, Poland
29
Stanford University, HEPL and KIPAC, Stanford, CA 94305-4085, USA
30
School of Chemistry & Physics, University of Adelaide, Adelaide 5005, Australia e-mail: growell@physics.adelaide.edu.au
31
Institut für Theoretische Physik, Lehrstuhl IV: Weltraum und Astrophysik, Ruhr-Universität Bochum, 44780 Bochum, Germany
Received:
17
March
2009
Accepted:
19
May
2009
Aims. Galaxy clusters are key targets in the search for ultra high energy particle accelerators. The Coma cluster represents one of the best candidates for such a search owing to its high mass, proximity, and the established non-thermal radio emission centred on the cluster core.
Methods. The HESS (High Energy Stereoscopic System) telescopes observed Coma for ~8 h in a search for γ-ray emission at energies >1 TeV. The large 3.5° FWHM field of view of HESS is ideal for viewing a range of targets at various sizes including the Coma cluster core, the radio-relic (1253+275) and merger/infall (NGC 4839) regions to the southwest, and features greater than away.
Results. No evidence for point-like nor extended TeV γ-ray emission was found and upper limits to the TeV flux for , >5, and >10 TeV were set for the Coma core and other regions. Converting these limits to an energy flux the lowest or most constraining is the TeV upper limit for the Coma core (0.2° radius) at ~8% Crab flux units or ph cm-2 s-1.
Conclusions. The upper limits for the Coma core were compared with a prediction for the γ-ray emission from proton-proton interactions, the level of which ultimately scales with the mass of the Coma cluster. A direct constraint using our most stringent limit for TeV, on the total energy content in non-thermal protons with injection energy spectrum and spatial distribution following the thermal gas in the cluster, is found to be ~0.2 times the thermal energy, or erg. The TeV γ-ray threshold in this case corresponds to cosmic-ray proton energies 50 TeV. Our upper limits rule out the most optimistic theoretical models for gamma ray emission from clusters and complement radio observations which constrain the cosmic ray content in clusters at significantly lower proton energies, subject to assumptions on the magnetic field strength.
Key words: gamma rays: observations / galaxies: clusters: individual: Coma (ACO 1656)
© ESO, 2009
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