Recent progress in the search for black holes in galactic nuclei

Massive nuclear black holes of 10^6 - 10^9 solar masses are believed to be responsible for the the energy production in quasars and active galaxies, and are thought to be present in many quiescent galaxies as well. Dynamical evidence for this can be sought by studying the dynamics of gas and stars in galactic nuclei at high spatial resolution. This paper reviews the current evidence, with emphasis on some recent developments and ongoing projects. The evidence from water masers and gas kinematics in the active galaxies NGC 4258 and M87 is compelling. In quiescent galaxies only stellar kinematics are generally available. One well-studied case is M32. Stellar dynamical f(E,L_z) models with a few million solar mass black hole fit the ground-based kinematical data remarkably well. N-body simulations of an edge-on f(E,L_z) model for M32 show that this model is stable. HST spectra should soon provide new and improved constraints on the presence of black holes in quiescent galaxies.