M 87 and cooling flows
The hot gas in M 87 is dense enough to have a cooling time that is significantly shorter than the Hubble time out to a radius r cool ∼ 70 kpc. For historical reasons this gas has often been assumed to be in a steady state in which gas sinks inwards until at some radius it condenses out into undetected compact objects. A considerable body of observational evidence now suggests that the gas, far from being in a steady state, is interacting violently with the AGN which it feeds. There are good observational and theoretical grounds for believing that the nuclear activity is episodic and that the enveloping plasma is in a highly dynamic state completely unlike that assumed in the classical cooling-flow picture.
KeywordsBlack Hole Accretion Disk Active Galactic Nucleus Compton Scattering Cool Flow
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