  HST observations show that the surface brightness profiles of early-type
galaxies have central cusps. I summarize here the results of van der Marel
(1999), which show that the observed characteristics of these cusps are
consistent with the hypothesis that all early-type galaxies have central black
holes (BHs) that grew adiabatically in homogeneous isothermal cores. The models
suggest a roughly linear correlation between BH mass and V-band galaxy
luminosity, log M_BH = -1.83 + log L in solar units, similar to the relation
suggested by kinematical BH detections in nearby galaxies.
