2008ApJ...687..193W

The next generation of neutrino and γ-ray detectors should provide new insights into the creation and propagation of high-energy protons within galaxy clusters, probing both the particle physics of cosmic rays interacting with the background medium and the mechanisms for high-energy particle production within the cluster. In this paper we examine the possible detection of γ-rays (via the GLAST satellite) and neutrinos (via the ICECUBE and Auger experiments) from the Coma cluster of galaxies, as well as for the γ-ray-bright clusters Abell 85, 1758, and 1914. These three were selected from their possible association with unidentified EGRET sources, so it is not yet entirely certain that their γ-rays are indeed produced diffusively within the intracluster medium, as opposed to active galactic nuclei. It is not obvious why these inconspicuous Abell clusters should be the first to be seen in γ-rays, but a possible reason is that all of them show direct evidence of recent or ongoing mergers. Their identification with the EGRET γ-ray sources is also supported by the close correlation between their radio and (purported) γ-ray fluxes. Under favorable conditions (including a proton spectral index of 2.5 in the case of Abell 85, and ∼2.3 for Coma, and Abell 1758 and 1914), we expect ICECUBE to make as many as 0.3 neutrino detections/yr from the Coma cluster of galaxies and as many as a few per year from the Abell clusters 85, 1758, and 1914. Also, Auger may detect as many as 2 events per decade at ∼10¹⁸ eV from these γ-ray-bright clusters.