  I use the fact that the radiation emitted by the accretion disk of
supermassive black hole can heat up the surrounding gas in the protogalaxy to
achieve hydrostatic equilibrium during the galaxy formation. The correlation
between the black hole mass M_BH and velocity dispersion \sigma thus naturally
arises. The result generally agrees with empirical fittings from observational
data, even with M_BH \leq 10^6M_sun. This model provides a clear picture on how
the properties of the galactic supermassive black holes are connected with the
kinetic properties of the galactic bulges.
