Speaker:
　　　 Jeremiah Ostriker
Time:
　　　 Sept.7th, 9:00AM
Location:
　　　 3th floor, small conf. room
Abstract:
Black holes in the centers of galaxies will be fed by accretion of ambient gas whenever gas reaches those central regions. This can be due to mergers, but even without mergers the evolution of the stellar populations of normal galaxies provides very large amounts of gas. Much of that gas will cool and fall to the centers of the systems, where it will induce starbursts and accretion events. We follow these events with a high resolution hydrodynamic code, allowing for radiative transfer, supernovae and other relevant physical processes. We find that the high energy output from these objects will strongly inhibit inflow, causing episodic accretion and a low “duty cycle”. The simulations help us to understand many phenomena including the black hole stellar mass relation, the paucity of gas in ellipticals, the incidence of the “K+A” phenomena and the observed fact that most of the black holes found in galactic centers are in the “off” state. In clusters of galaxies this feedback helps to reduce and regulate “cooling flows”.