Institute of Astronomy

Feedback from Accreting Black Holes: The Importance of Momentum Driving

SpeakerTalk DateTalk Series
Jeremiah Ostriker, Princeton17 May 2012Institute of Astronomy Colloquia


lack holes, in the centers of galaxies, are fed by accretion of ambient gas, whenever gas reaches those central regions due either to mergers, or as the result of normal stellar evolution. That gas will cool and fall to the centers of the systems, where it will induce starbursts and accretion events onto the black holes. This causes outbursts of UV from the BH discs, X-rays from coronal gas and polar, radiation driven winds, with the efficiencies in these three categories roughly 10-1, 10-2 & 10-3. The mass, momentum and energy in these outbursts can have dramatic consequences for the growth of the BH and for the ambient galaxy. Most AGN feedback treatments do not include the mass and momentum components. We follow these events with 1D, 2D and 3D hydrodynamic codes. BH growth is similar to what has been found by others, but the momentum driving produces much more energetic winds than does thermal feedback. Observable consequences include the AGN absorption lines, shock accelerated, synchrotron emitting particles and wind driven bubbles in the IGM. In addition, we find that the feedback strongly inhibits inflow, causing episodic accretion. The simulations help us to understand many phenomena, including the black hole stellar mass relation, the paucity of gas in ellipticals, and the observed fact that most of the black holes found in galactic centers are found in the “off” state.


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