A Fundamental Relation between Supermassive Black Holes and Their Host Galaxies

The masses of supermassive black holes correlate almost perfectly with the velocity dispersions of their host bulges, M_bh~σ^α, where α=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 recently estimated by Magorrian et al. lie systematically above the M_bh-σ relation defined by more accurate mass estimates, some by as much as 2 orders of magnitude. The tightness of the M_bh-σ relation implies a strong link between black hole formation and the properties of the stellar bulge.