UCDs as Probes of the Major and Minor Merger Histories of Galaxies

Abstract

Two competing theories posit that Ultra Compact Dwarfs (UCDs) form either as the stripped nuclei of dwarf galaxies or as giant globular clusters (GGCs) associated with the largest globular cluster (GC) systems. By focussing on the field and group environments where young UCDs may be most common, we have discovered the first UCD that is clearly the result of recent (<4 Gyr ago) stripping of a companion galaxy. However, we have also found a definitive case of a multiple-UCD system created via GC formation processes, which are likely associated with major galaxy mergers. We demonstrate that it is possible to reliably distinguish the two types of UCD, thereby probing both the major and minor merger histories of individual galaxies.