  We discuss the role of feedback via photoionization and Compton heating in
the co-evolution of massive black holes at the center of spheroidal galaxies
and their stellar and gaseous components. We first assess the energetics of the
radiative feedback from a typical quasar on the ambient interstellar gas. We
then demonstrate that the observed Mbh-sigma relation could be established at a
relatively early epoch in galactic evolution when the formation of the stellar
bulge was almost completed and the gas-to-stars mass ratio was reduced to a low
level ~0.01 such that cooling could not keep up with radiative heating. A
considerable amount of gas was expelled at that time and black hole accretion
proceeded at a much lower rate thereafter.
