The Nature of the Black Hole in a NGC 4472 Globular Cluster and the Origin of Its Broad [OIII] Emission

We propose to use STIS to obtain optical spectroscopy at high spatial resolution of the black hole-hosting globular cluster RZ2109 in the Virgo elliptical NGC 4472. This is motivated by our very recent discovery broad [OIII] 4959, 5007 emission with a width of several thousand km/s in this globular cluster. The STIS spectroscopy will enable us to determine if the very broad [OIII] emission is due to material driven at high velocity from the central accreting black hole across the globular cluster, or if the velocity widths are due to gravitational motions very close to the central black hole. In the former case, the [OIII] emission should extend over a few-tenths of an arcsecond and be spatially resolved by HST and STIS, while in the latter case, the emission lines will be unresolved. Distinguishing between these two possibilities will allow us to - 1} determine whether the black hole is of intermediate mass or a stellar mass, and thereby whether the black hole mass - sigma relation extends to globular cluster masses, 2} test models of black hole formation and evolution in dense stellar systems, and 3} address the nature of accretion in the high luminosity black-hole X-ray source, and constrain the feedback processes from luminous black holes into their surrounding medium in dense stellar systems.