Models for the Relativistic Electron Population and Nonthermal Emission in Clusters of Galaxies

Abstract

Models for the integrated relativistic electron population in clusters of galaxies are presented. The results depend on the history of electron acceleration in the cluster. If there is no present particle acceleration or other sources, then no high energy electrons (gamma >~ 300, E >~ 150 MeV) should be present due to inverse Compton (IC) losses. High energy electrons are present if particle acceleration is occurring at present, perhaps as a result of a cluster merger shock. The resulting IC, synchrotron, and gamma-ray emission from these models has been calculated. In the models, extreme ultraviolet (EUV) and very soft X-ray emission are a nearly ubiquitous feature, because this emission comes from IC by electrons with the longest lifetimes in clusters. Diffuse UV and optical emission is also expected in most clusters, but at levels which will be difficult to observe. Hard X-ray tails and diffuse radio synchrotron emission are only expected in clusters with recent or current particle acceleration; for example, this acceleration might be due to intracluster merger shocks. Gamma-ray observations at energies of around 100 MeV should detect both the dominant population of relativistic electrons and the corresponding ions. The predicted fluxes are easily detectable with GLAST.