Non-thermal emission from Galaxy Clusters and future observations with the FERMI gamma-ray telescope and LOFAR

TL;DR

This paper discusses the expected non-thermal gamma-ray and radio emissions from galaxy clusters, emphasizing the potential insights from upcoming FERMI and LOFAR observations into relativistic particles and magnetic fields within clusters.

Contribution

It presents theoretical predictions of gamma-ray and radio emissions from galaxy clusters based on re-acceleration models involving relativistic particles and MHD turbulence during mergers.

Findings

Gamma-ray emission is expected to be common in galaxy clusters.

Diffuse radio emission correlates with cluster mergers.

Upcoming observations will test these non-thermal emission models.

Abstract

FERMI (formely GLAST) and LOFAR will shortly provide crucial information on the non-thermal components (relativistic particles and magnetic field) in galaxy clusters. After discussing observational facts that already put constraints on the properties and origin of non-thermal components, I will report on the emission spectrum from galaxy clusters as expected in the context of general calculations in which relativistic particles (protons and secondary electrons due to proton-proton collisions) interact with MHD turbulence generated in the cluster volume during cluster-cluster mergers. In this scenario (known as re-acceleration scenario) diffuse cluster-scale radio emission is produced in massive clusters during merging events, while gamma ray emission, at some level, is expected to be common in clusters. Expectations of interest for LOFAR and FERMI are also briefly discussed.