Effects of Massive Central Black Holes on Dense Stellar Systems

Abstract

The paper discusses some dynamical and astrophysical consequences of the idea that a massive black hole may be present at the centers of globular star clusters or galactic nuclei. The formation of a power-law cusp in the stellar density distribution of a globular cluster is analyzed, the rate at which stars in the cusp are swallowed or disrupted by the black hole is estimated, and probable observable manifestations of these processes are considered. It is argued that most stars on orbits with radii less than or approximately equal to some defined 'critical radius' will diffuse into low-angular-momentum 'loss-cone' orbits on a timescale comparable to the stellar relaxation time in the cluster core and will ultimately be swallowed by the black hole. The results are applied to Hills' (1975) model of a galactic nucleus containing a black hole of at least 10 million solar masses.