New results from H.E.S.S. observations of galaxy clusters
arXiv:0907.3001 · doi:10.1142/S021827180901545X
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.
4 pages, one figure, invited talk at the 2nd Heidelberg workshop: "High-Energy Gamma-rays and Neutrinos from Extra-Galactic Sources", January 13 - 16, 2009, to be published in Int. J. Mod. Phys. D
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- On the Physics of Radio Halos in Galaxy Clusters: Scaling Relations and Luminosity Functions
- Constraints on diffuse gamma-ray emission from structure formation processes in the Coma cluster
- Constraining Cosmic Rays and Magnetic Fields in the Perseus Galaxy Cluster with TeV observations by the MAGIC telescopes
- Deep observation of the NGC 1275 region with MAGIC: search of diffuse gamma-ray emission from cosmic rays in the Perseus cluster
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- Simulating X-ray Supercavities and Their Impact on Galaxy Clusters
- Constraining the cosmic-ray pressure in the inner Virgo Cluster using H.E.S.S. observations of M 87