Gamma-ray emission from clusters of galaxies - a competition between cosmic rays and dark matter
Clusters of galaxies are expected to be significant gamma-ray emitters with contributions from both annihilating dark matter (DM) and the cosmic-ray (CR) proton induced pions that decay into gamma-rays. Besides establishing an entirely new class of sources, gamma-ray observations of clusters open up a unique window for studying the physics of high energy, non-thermal processes in cosmic large-scale environments. I use a selection of supersymmetric DM models and estimate the gamma-ray flux from various emission processes. To extend these predictions for nearby galaxy clusters, I present a CR model that allows us to reliably predict both the spatial and spectral emission profiles from pion decay and inverse Compton. I identify the brightest clusters for both Fermi-LAT and current imaging air Cherenkov telescopes, and use gamma-ray observations to constrain CR- and cluster-physics as well as the expected boost of annihilating DM from substructures.
