  The masses of supermassive black holes correlate almost perfectly with the
velocity dispersions of their host bulges, M(BH) ~ sigma^alpha, where alpha
=4.8 +/- 0.5$. The relation is much tighter than the relation between M(BH) and
bulge luminosity, with a scatter no larger than expected on the basis of
measurement error alone. Black hole masses estimated by Magorrian et al. (1998)
lie systematically above the M(BH)-sigma relation defined by more accurate mass
estimates, some by as much as two orders of magnitude. The tightness of the
M(BH)-sigma relation implies a strong link between black hole formation and the
properties of the stellar bulge.
