Feedback from Supermassive Black Holes

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Supermassive black holes (SMBHs) residing in the centers of galaxy clusters release a huge amount of energy impacting their surroundings. This released energy prevents rapid radiative cooling of the gas and quenches star formation in massive central galaxies. Understanding feedback from such active galactic nuclei (AGN) is, therefore, essential for modeling galaxy evolution.

A commonly-accepted model of AGN feedback posits that SMBHs eject material outflows that usually manifest themselves as bubbles filled with relativistic particles. These bubbles appear as depressions or cavities in the X-ray images of massive galaxies and galaxy clusters. The power of these outflows is sufficient to offset gas cooling losses. It is unclear, however, how the energy from bubbles is transferred to the intracluster medium and how it is mixed within the cluster core regions.

In my research, I use (mainly) X-ray data from Chandra, XMM-Newton and Hitomi satellites as well as numerical simulations, to understand the physical mechanisms responsible for the energy transport from SMBHs to the intracluster medium.  

X-ray images of the Perseus (top) and Virgo (bottom) galaxy clusters divided by the models of surface brightness to emphasize gas perturbations. The brightest central regions are dominated by the AGN activity that inflates bubbles of relativistic plasma, creates shocks and prominent gas outflows. Credit: NASA/CXC/Stanford/I.Zhuravleva et al. 


Turbulent heating versus gas cooling rates in the Perseus and Virgo cores calculated in a set of annuli (shaded regions). The turbulent heating rate is calculated from the analysis of X-ray surface brightness fluctuations. There is an approximate balance between the heating and cooling, suggesting that turbulence may be the key mechanism responsible for compensating gas cooling losses. Credit: Zhuravleva I. et al., Nature, 515, 85, 2014.