Structure of the globular cluster M15 and constraints on a massive central black hole

Abstract

Globular clusters could harbor massive central black holes (BHs), just as galaxies do. So far, no unambiguous detection of a massive BH has been reported for any globular cluster. However, the dense core-collapsed cluster M15 seems to be a good candidate. I review the available photometric and kinematic data for this cluster. Both are consistent with a BH of approximately 2000 solar masses, although such a BH is not unambiguously required by the data. I discuss some ongoing studies with Keck and HST which should shed more light on this issue in the coming years.