Scaling relations in galaxy groups and clusters: defining and breaking

I present results from a number of projects involving both theoretical and observational investigations of galaxy clusters. Firstly, using a sample of galaxy clusters spanning 2 orders of magnitude in mass, extracted from high resolution numerical simulations, I will present baseline expectations for self-similar X-ray M-T scaling relations. These are calculated at a range of density contrasts, derived from both fixed
density contrasts and from contrasts derived from the top-hat model. Secondly, I will present a Chandra and VLA study of a galaxy group which hosts a young restarting radio galaxy, embedded in older emission, where the new source is driving a Mach 2.4 shock into its surroundings and the old source can counteract radiative losses. We demonstrate for the first time that feedback regulated radio galaxies can not only regulate catastrophic cooling in galaxy groups/clusters but also increase the entropy of the ISM, leading to a breaking of the scaling relations.

Nazirah Jetha

CEA Saclay