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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 the
self-gravity of the dark matter and gas components, our approach includes the
radiative cooling and photoheating of the gas, as well as a subresolution
multiphase model for star formation and supernova feedback. Additionally, we
incorporate a periodic heating mechanism in the form of hot, buoyant bubbles,
injected into the intragalactic medium (IGM) during the active phases of the
accreting central AGN. We use simulations of isolated cluster halos of
different masses 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 for the energy injection
mechanism, in order to obtain better constraints on the underlying physical
picture. We argue that AGN heating can substantially affect the properties of
both the stellar and gaseous components of clusters of galaxies. Most
importantly, it alters the properties of the central dominant (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 galaxy, giving it red stellar colours as observed.Comment: 22 pages, 15 figures, minor revisions, MNRAS accepte
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