Hydrodynamical simulations of cluster formation with central AGN heating

We analyse a hydrodynamical simulation model for the recurrent heating of the central intracluster medium (ICM) by active galactic nuclei (AGN). Besides self-gravity of a dark matter and a gas component, our approach includes radiative cooling and photo-heating of the gas, as well as a subresolution multiphase model for star formation and SNe feedback. Additionally, we incorporate a periodic heating mechanism in the form of hot, buoyant bubbles, injected into the intra-galactic medium during the active phases of accreting central AGN. We use simulations of isolated cluster halos of different mass to study the bubble dynamics and the heat transport into the IGM. We also apply our model to self-consistent cosmological simulations of the formation of galaxy clusters with a range of masses. Our numerical schemes explore a variety of different assumptions for the spatial configuration of AGN-driven bubbles, for their duty cycles and the energy injection mechanism, in order to better constrain the underlying physical picture. We argue that AGN heating can substantially affect the properties both of the stellar and gaseous components of clusters of galaxies. Most importantly, it alters the properties of the central cD galaxy by reducing the mass deposition rate of freshly cooled gas out of the ICM, thereby offering an energetically plausible solution to the cooling flow problem. At the same time, this leads to reduced or eliminated star formation in the central cD, giving it red stellar colours as observed.