Formation of ultra-compact dwarf galaxies from supergiant molecular
  clouds
  The origin of ultra-compact dwarf galaxies (UCDs) is not yet clear. One
possible formation path of UCDs is the threshing of a nucleated elliptical
dwarf galaxy (dE, N), however, it remains unclear how such massive nuclear
stellar systems were formed in dwarf galaxies. To better establish the early
history of UCDs, we investigate the formation of UCD progenitor clusters from
super giant molecular clouds (SGMCs), using hydrodynamical simulations. In this
study we focus on SGMCs with masses $10^{7} - 10^{8} \rm M_{\odot}$ that can
form massive star clusters that display physical properties similar to UCDs. We
find that the clusters have extended star formation histories with two phases,
producing multiple distinct stellar populations, and that the star formation
rate is dependent on the feedback effects of SNe and AGB stars. The later
generations of stars formed in these clusters are more compact, leading to a
clearly nested structure, and these stars will be more He-rich than those of
the first generation, leading to a slight colour gradient. The simulated
clusters demonstrate scaling relations between $R_{\rm eff}$ and $M$ and
$\sigma_{v}$ and $M$ consistent with those observed in UCDs and strongly
consistent with those of the original SGMC. We discuss whether SGMCs such as
these can be formed through merging of self-gravitating molecular clouds in
galaxies at high-z.
