Sowing the seeds of massive black holes in small galaxies: Young
  clusters as the building blocks of Ultra-Compact-Dwarf Galaxies
  Interacting galaxies often have complexes of hundreds of young stellar
clusters of individual masses $\sim 10^{4-6}~M_\odot$ in regions that are a few
hundred parsecs across. These cluster complexes interact dynamically, and their
coalescence is a candidate for the origin of some ultracompact dwarf galaxies
(UCDs). Individual clusters with short relaxation times are candidates for the
production of intermediate-mass black holes of a few hundred solar masses, via
runaway stellar collisions prior to the first supernovae in a cluster. It is
therefore possible that a cluster complex hosts multiple intermediate-mass
black holes that may be ejected from their individual clusters due to mergers
or binary processes, but bound to the complex as a whole. Here we explore the
dynamical interaction between initially free-flying massive black holes and
clusters in an evolving cluster complex. We find that, after hitting some
clusters, it is plausible that the massive black hole will be captured in an
ultracompact dwarf forming near the center of the complex. In the process, the
hole typically triggers electromagnetic flares via stellar disruptions, and is
also likely to be a prominent source of gravitational radiation for the
advanced ground-based detectors LIGO and VIRGO. We also discuss other
implications of this scenario, notably that the central black hole could be
considerably larger than expected in other formation scenarios for ultracompact
dwarfs.
