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

TL;DR

This paper investigates Ultra Compact Dwarfs (UCDs) to understand galaxy merger histories, distinguishing between those formed by galaxy stripping and those formed as globular clusters, revealing recent galaxy interactions.

Contribution

It introduces a method to differentiate UCD origins, enabling insights into both major and minor galaxy merger events.

Findings

First clear case of a UCD from recent galaxy stripping.

Identification of a multiple-UCD system formed via globular cluster processes.

Demonstration of reliable UCD origin classification.

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.