Publications of the Astronomical Society of Australia

Research Article

Ultra-Compact Dwarf Galaxies in Galaxy Clusters

Michael J. Drinkwatera1 c1, Michael D. Gregga2a3, Warrick J. Coucha4, Henry C. Fergusona5, Michael Hilkera6, J. Bryn Jonesa7, Arna Karicka8 and Steven Phillippsa9

a1 Department of Physics, University of Queensland, Brisbane QLD 4072, Australia

a2 Department of Physics, University of California, Davis, CA 95616, USA

a3 Institute for Geophysics and Planetary Physics, Lawrence Livermore National Laboratory, L-413, Livermore, CA 94550, USA

a4 School of Physics, University of New SouthWales, Sydney NSW 2052, Australia

a5 Space Telescope Science Institute, 3700 San Martin Dve, Baltimore, MD 21218, USA

a6 Sternwarte der Universität Bonn, 53121 Bonn, Germany

a7 School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK

a8 School of Physics, University of Melbourne, Melbourne VIC 3010, Australia

a9 Astrophysics Group, Department of Physics, University of Bristol, Bristol BS8 1TL, UK


We review the evidence that the ultra-compact dwarf (UCD) galaxies we recently discovered in the Fornax Cluster form a new, previously unknown class of galaxies and we discuss possible scenarios for their formation. We then present recent results that UCDs are also present in the Virgo Cluster, and that there is a much larger than expected population of fainter UCDs in the Fornax Cluster. The size and properties of this population may lead us to revise our original ‘galaxy threshing’ hypothesis for the formation of UCDs.

(Received May 03 2004)

(Accepted September 27 2004)


  • globular clusters: general;
  • galaxies: dwarf;
  • galaxies: formation;
  • galaxies: clusters: general


c1 Corresponding author. Email: