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arXiv · 0907.3001

New results from H.E.S.S. observations of galaxy clusters

W. Domainko·D. Nedbal·J. A. Hinton·O. Martineau-Huynh
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Abstract

Clusters of galaxies are believed to contain a significant population of cosmic rays. From the radio and probably hard X-ray bands it is known that clusters are the spatially most extended emitters of non-thermal radiation in the Universe. Due to their content of cosmic rays, galaxy clusters are also potential sources of VHE (>100 GeV) gamma rays. Recently, the massive, nearby cluster Abell 85 has been observed with the H.E.S.S. experiment in VHE gamma rays with a very deep exposure as part of an ongoing campaign. No significant gamma-ray signal has been found at the position of the cluster. The non-detection of this object with H.E.S.S. constrains the total energy of cosmic rays in this system. For a hard spectral index of the cosmic rays of -2.1 and if the cosmic-ray energy density follows the large scale gas density profile, the limit on the fraction of energy in these non-thermal particles with respect to the total thermal energy of the intra-cluster medium is 8% for this particular cluster. This value is at the lower bounds of model predictions.

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W. Domainko, D. Nedbal, J. A. Hinton, O. Martineau-Huynh. 2009-07-17. New results from H.E.S.S. observations of galaxy clusters. https://doi.org/10.1142/s021827180901545x

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