Mapping out the origins of compact stellar systems
  We present a suite of extragalactic explorations of the origins and nature of
globular clusters (GCs) and ultra-compact dwarfs (UCDs), and the connections
between them. An example of GC metallicity bimodality is shown to reflect
underlying, distinct metal-poor and metal-rich stellar halo populations.
Metallicity-matching methods are used to trace the birth sites and epochs of
GCs in giant E/S0s, pointing to clumpy disk galaxies at z ~ 3 for the
metal-rich GCs, and to a combination of accreted and in-situ formation modes at
z ~ 5-6 for the metal-poor GCs. An increasingly diverse zoo of compact stellar
systems is being discovered, including objects that bridge the gaps between
UCDs and faint fuzzies, and between UCDs and compact ellipticals. Many of these
have properties pointing to origins as the stripped nuclei of larger galaxies,
and a smoking-gun example is presented of an omega Cen-like star cluster
embedded in a tidal stream.
