Department of Astronomy Colloquium Series Presents:

How AGN Feedback Might Work

One of the biggest challenges to understanding how galaxies work is decoding the role of the central supermassive black hole. Without feedback from the black hole (“AGN feedback”), galaxy evolution models fail to produce realistic massive galaxies and galaxy clusters. Somehow, accretion of matter onto the central black hole of a massive galaxy is tuned so that it regulates radiative cooling and the condensation of gas in a volume of space many orders of magnitude larger than the zone of gravitational influence around a black hole. The effects of these black holes is most easily seen in the observations of the most massive galaxies in the universe, the central galaxies of galaxy clusters. Strong observational evidence now indicates the activity of the AGN is closely coupled to the thermodynamic state of the circumgalactic medium, where most of a galaxy’s baryons reside. I will discuss how this relationship could arise and how a feedback mechanism that maintains the circumgalactic medium in a marginally unstable state can regulate star formation within galaxies.