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 0.05 L _ { Edd } and momentum rates \sim 20 L _ { 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 ^ { -1 } and mass outflow rates up to 4000 ~ { } M _ { \odot } { yr } ^ { -1 } 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 .