Testing the tidal stripping scenario of ultra-compact dwarf galaxy
  formation by using internal properties
  We use the hydrodynamical EAGLE simulation to test if ultra-compact dwarf
galaxies (UCDs) can form by tidal stripping by predicting the ages and
metallicities of tidally stripped galaxy nuclei in massive galaxy clusters, and
compare these results to compiled observations of age and metallicities of
observed UCDs. We further calculate the colours of our sample of simulated
stripped nuclei using SSP models and compare these colours to observations of
UCDs in the Virgo cluster. We find that the ages of observed UCDs are
consistent with simulated stripped nuclei, with both groups of objects having a
mean age > 9 Gyr. Both stripped nuclei and UCDs follow a similar
mass-metallicity relationship, and the metallicities of observed UCDs are
consistent with those of simulated stripped nuclei for objects with M >
$10^{7}~M_{\odot}$. The colours of observed UCDs are also consistent with our
simulated stripped nuclei, for objects with M > $10^{7}~M_{\odot}$, with more
massive objects being redder. We find that the colours of stripped nuclei
exhibit a bimodal red and blue distribution that can be explained by the
dependency of colour on age and metallicity, and by the mass-colour relation.
We additionally find that our low mass stripped nuclei sample is consistent
with the colour of blue globular clusters. We conclude that the internal
properties of simulated nuclei support the tidal stripping model of UCD
formation.
