Dr. Feng Yuan (SHAO) visit our group and give colloquium speech

Sep 24, 2010

“AGN Feedback at Sub-pc Scale”

The hot accretion flow is usually optically thin in the radial direction, therefore the photons produced at one radius can travel for a long distance without being absorbed. These photons can thus heat or cool electrons at other radii via Compton scattering. This effect has been ignored in most previous works.

After taking into account this effect, we find that when the luminosity (or accretion rate) is higher than about 1% Eddington luminosity, we are not able to get the self-consistent accretion solution, because the equilibrium temperature of electrons at large radii is higher than the virial temperature as a result of strong Compton heating, so the accretion is suppressed. In this case the activity of the black hole will likely “oscillate” between an active and an inactive phase. Based on this mechanism we successfully explain the intermittent activity of some compact radio sources.