Large--Scale Outflows in Galaxies
  We discuss massive outflows in galaxy bulges, particularly ones driven by
accretion episodes where the central supermassive black hole reaches the
Eddington limit. We show that the quasar radiation field Compton--cools the
wind shock until this reaches distances $\sim 1$ kpc from the black hole, but
becomes too dilute to do this at larger radii. Radiative processes cannot cool
the shocked gas within the flow time at any radius. Outflows are therefore
momentum-driven at small radii (as required to explain the $M - \sigma$
relation). At large radii they are energy-driven, contrary to recent claims.
  We solve analytically the motion of an energy--driven shell after the central
source has turned off. This shows that the thermal energy in the shocked wind
can drive further expansion for a time $\sim 10$ times longer than the active
time of the central source. Outflows observed at large radii with no active
central source probably result from an earlier short (few Myr) active phase of
this source.
