Intermediate-Mass Black Holes in Extragalactic Globular Clusters
  Intermediate-mass black holes (IMBHs) have masses of about 100 to 100,000
solar masses. They remain elusive. Observing IMBHs in present-day globular
clusters (GCs) would validate a formation channel for seed black holes in the
early universe and inform event predictions for gravitational wave facilities.
Reaching a large number of GCs per galaxy is key, as models predict that only a
few percent will have retained their gravitational-wave fostering IMBHs.
Related, many galaxies will need to be examined to establish a robust sample of
IMBHs in GCs. These needs can be meet by using a next-generation Very Large
Array (ngVLA) to search for IMBHs in the GCs of hundreds of galaxies out to a
distance of 25 Mpc. These galaxies hold tens of thousands of GCs in total. We
describe how to convert an ngVLA signal from a GC to an IMBH mass according to
a semi-empirical accretion model. Simulations of gas flows in GCs would help to
improve the robustness of the conversion. Also, self-consistent dynamical
models of GCs, with stellar and binary evolution in the presence of IMBHs,
would help to improve IMBH retention predictions for present-day GCs.
