Heating galaxy clusters with interacting dark matter

Abstract

ABSTRACT The overcooling of cool core clusters is a persistent puzzle in the astrophysics of galaxy clusters. We propose that it may naturally be resolved via interactions between the baryons of the intracluster medium (ICM) and its dark matter (DM). DM–baryon interactions can inject heat into the ICM to offset bremsstrahlung cooling, but these interactions are also strongly constrained by existing experiments and astrophysical observations. We survey existing constraints and combine these with the energetic needs of an observed sample of cool core clusters. We find that a robust parameter space exists for baryon–DM scattering solutions to the cooling flow problem, provided that only a sub-component of DM interacts strongly with the baryons. Interestingly, baryon–DM scattering is a thermally stable heating source so long as the baryon temperature is greater than 1/3 to 1/2 the DM temperature, a condition that seems to be satisfied observationally.