AGN Feedback

Black holes have a significant impact on their environment. Over the past 10 years, a consesus has emerged that galaxy clusters are heated by the action of relativistic jets, blasting into the intergalactic medium from the supermassive black hole of the central massive elliptical galaxy of the cluster. This heating might be enough to counter-balance the radiative losses the cluster gas is experiencing constantly, as it emits X-rays that can be observed from space based X-ray telescopes.

How this heating occurs and whether the heat can, in fact, be distributed to just the right locations in the cluster is still an issue of contentious debate. We are running state-of-the-art hydro simulations of galaxy clusters under the influence of energy injection from a central jet. We use fully cosmologically evolved clusters and inject powerful, collimated jets into them from the cluster center. A movie of this process can be accessed from Fig. 2. The key difference to earlier studies is that we include, for the first time, the dynamic state of the cluster, rather than assuming that it is a spherically symmetric, hydro-static atmosphere. This has important consequences for the dynamical evolution of radio sources (jets and the large scale bubbles of hot gas they blow into the intergalactic medium).

One of the important early results is that internal cluster dynamics, excited both by the action of the jets themselves and simply due to residual motions from previous dynamical encounters, as well as turbulence induced by cluster substructure (e.g., moving galaxies) can redistribute the gas in the cluster center in such a way that it erases any channels that were previously carved by the jet. This means that subsequent powerful jet outbursts can efficiently couple with the dense gas of the inner cluster, making it possible for the jet to heat the gas that needs it most (the coldest gas near the center of the cluster).