AGN Winds and the Black-Hole - Galaxy Connection

Abstract

During the last decade, wide-angle powerful outflows from AGN, both on parsec and kpc scales, have been detected in many galaxies. These outflows are widely suspected to be responsible for sweeping galaxies clear of their gas. We present the analytical model describing the propagation of such outflows and calculate their observable properties. Large-scale AGN-driven outflows should have kinetic luminosities \sim {\eta}L_Edd/2 \sim 0.05L_Edd and momentum rates \sim 20L_Edd/c, where L_Edd is the Eddington luminosity of the central black hole and {\eta} \sim 0.1 its radiative accretion efficiency. This creates an expanding two-phase medium in which molecular species coexist with hot gas, which can persist after the central AGN has switched off. This picture predicts outflow velocities \sim 1000 - 1500 km/s and mass outflow rates up to 4000 M_\odot/yr on kpc scales, fixed mainly by the host galaxy velocity dispersion (or equivalently black hole mass). We compare our prediction with recent observational data, finding excellent agreement, and suggest future observational tests of this picture.