Ultra-Compact Dwarf Galaxies and Globular Clusters: A Review of Their Spatial and Dynamical Properties

The discovery of ultra compact dwarf (UCD) galaxies has been very well reviewed by Michael Hilker in these proceedings. Here we wish to focus on the large-scale distribution of UCDs. Our study was originally motivated by a search for "M32-type" compact elliptical galaxies in the Fornax Cluster. We didn't find any of these, but we did demonstrate that morphological membership classification can overlook many compact dwarf cluster members [3]. This motivated the 2dF Fornax Cluster Spectroscopic Survey (FCSS, [4]), which measured redshifts of all objects, both "stars" and "galaxies" in the cluster centre, resulting in the detection of 5 UCDs ([5] and also [9]). High resolution imaging and spectroscopy have since established that the most luminous UCDs are a new type of object [6]. We have extended our UCD searches to fainter limits [71, finding a total of 62 compact objects filling a large region of intra-cluster space (see Fig. 1). We discuss the distribution of these objects below, noting that our working UCD definition (Fornax Cluster members barely resolved in photographic survey data with m(Bj) < 21.5 mag) may also include genuine globular clusters (GCS).