Thermal wind from hot accretion flows at large radii

Abstract

We study slowly rotating accretion flow at parsec and subparsec scales irradiated by lowluminosity active galactic nuclei. We take into account the Compton heating, photoionization heating by the central X-rays. The bremsstrahlung cooling, recombination, and line cooling are also included.We find that due to the Compton heating, wind can be thermally driven. The power of wind is in the range (10-6-10-3) LEdd, with LEdd being the Eddington luminosity. The mass flux of wind is in the range (0.01 - 1) M˙Edd (M˙Edd = LEdd/0.1c2 is the Eddington accretion rate, c is speed of light).We define the wind generation efficiency as ∈ = PW/M˙BHc2, with PW being wind power,M˙BH being the mass accretion rate on to the black hole. ∈ lies in the range 10-4-1.18. Wind production efficiency decreases with increasing mass accretion rate. The possible role of the thermally driven wind in the active galactic feedback is briefly discussed.