Do Massive Black Holes Come in Small Packages? A census of black holes in compact stellar systems in the Virgo cluster.

The black hole (BH) mass function (MF) in the local universe - a fundamental measure of the origin and growth of BHs over Cosmic time - remains poorly constrained at intermediate masses. The very existence of BHs in this mass range is debated, but likely hosts include low-mass dwarf galaxies, for which the occupation fraction of BHs is an important ingredient for competing theories on supermassive BH (SMBH) formation. Observational challenges limit available avenues to search for BHs in dwarfs, but one under-utilized strategy is to infer the presence of central BHs by their dynamical influence on the cores of compact stellar systems (CSSs) including globular clusters, nuclear star clusters, ultra-compact dwarf galaxies (UCDs), and compact elliptical galaxies. CSSs have interconnected (often galactic) formation histories, and this technique has recently been successful in detecting SMBHs in several nearby UCDs, thereby proving their galactic origins as the remnant nuclei of former dwarf galaxies tidally stripped of their outer stellar sheaths. With the launch of JWST a systematic census of BHs in CSSs possible, as similar studies are prohibitively expensive using current ground or space-based facilities. To capitalize on JWST's capabilities we propose to use NIRSpec+IFU to obtain spatially-resolved stellar kinematics of 18 carefully selected CSSs crossing nearly four decades in mass, and located in a single cluster environment (Virgo). The R~2700 spectral datacubes will reveal dynamical fingerprints of BHs with masses >~10^5.5 Msun, providing enw insights into the occupation fraction of BHs in low-mass systems, and critical information on the origin of both CSSs and SMBHs.