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

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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http://hal.in2p3.fr/in2p3-00430248
Contributor : Swarna Bassava <>
Submitted on : Friday, November 6, 2009 - 12:01:53 PM
Last modification on : Friday, April 10, 2020 - 5:28:09 PM

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  • HAL Id : in2p3-00430248, version 1
  • ARXIV : 0907.3001

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O. Martineau-Huynh. New results from H.E.S.S. observations of galaxy clusters. 2009. ⟨in2p3-00430248⟩

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