H.E.S.S. observations of galaxy clusters

TL;DR

This paper reports on H.E.S.S. observations of galaxy clusters, aiming to detect very high energy gamma rays from cosmic ray interactions, and provides upper limits for specific clusters, contributing to understanding cosmic ray populations in clusters.

Contribution

First H.E.S.S. observations of galaxy clusters providing upper limits on VHE gamma-ray emission, advancing constraints on cosmic ray content in clusters.

Findings

Upper limits set for Abell 496 and Coma clusters.

No significant VHE gamma-ray detection observed.

Results constrain models of cosmic ray acceleration in clusters.

Abstract

Clusters of galaxies, the largest gravitationally bound objects in the universe, are expected to contain a significant population of hadronic and leptonic cosmic rays. Potential sources for these particles are merger and accretion shocks, starburst driven galactic winds and radio galaxies. Furthermore, since galaxy clusters confine cosmic ray protons up to energies of at least 1 PeV for a time longer than the Hubble time they act as storehouses and accumulate all the hadronic particles which are accelerated within them. Consequently clusters of galaxies are potential sources of VHE (> 100 GeV) gamma rays. Motivated by these considerations, promising galaxy clusters are observed with the H.E.S.S. experiment as part of an ongoing campaign. Here, upper limits for the VHE gamma ray emission for the Abell 496 and Coma cluster systems are reported.