Schedule Oct 02, 2009
Gamma-Ray Emission from Clusters of Galaxies - Cosmic Rays versus Dark Matter
Anders Pinzke (Stockholm Univ.)

Clusters of galaxies are expected to be significant gamma-ray emitters with contributions from both, annihilating dark matter (DM) and radiative processes induced by cosmic-rays (CRs). We present high-resolution hydrodynamical simulations of galaxy clusters at different dynamical stages using self-consistent CR physics in combination with radiative hydrodynamics. An improved spectral description of the CRs allows us to reliably predict both the spatial and spectral emission profiles from various CR processes. Besides establishing an entirely new class of sources, gamma-ray observations of clusters should open up a unique window for studying the physics of high energy, non-thermal processes in cosmic large-scale environments. Using a DM model that fits the recent electron and positron data from Fermi, PAMELA, and HESS with remarkable precision, we predict an observable level of gamma-rays from nearby galaxy clusters for the Fermi satellite. In order not to overproduce the EGRET upper limit on the gamma-ray emission from Virgo, we constrain the minimum mass of substructures in dark matter halos to be three orders of magnitudes larger than the expectation from cold dark matter scenarios in this particular DM model. This demonstrates that high-energy gamma-ray observations can act as a microscope for the smallest cosmological structures.

Author entry (protected)