AAO Colloquium.


Thursday 26 June 2003

3:30pm AAO Conference Room

Origin of Ultra-Compact Galactic Objects

Kenji Bekki, UNSW

Recent spectroscopic and morphological observational studies of galaxies around NGC1399 in the Fornax Cluster have discovered several `ultra-compact dwarf' (UCD) galaxies with intrinsic sizes of ~100 pc and absolute B-band magnitudes ranging from -13 to -11 mag. Based on the comparison between numerical simulations and recent photometric and spectroscopic observations of UCDs, I discuss (1) whether these UCDs originate from nucleated dwarf galaxies (dE,Ns) orbiting the Fornax cluster, (2) how dE,Ns can be formed in clusters of galaxies, and (3) whether there can be UCDs in group/field environments. I also discuss the physical relationships between the giant globular clusters of Omega Centauri and G1 and UCDs. I propose that Omega Centauri can be formed from an early tidal interaction between the young Galactic disk and an ancient dE,N orbiting the Galaxy.