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The HST/ACS Coma Cluster Survey – V. Compact stellar systems in the Coma Cluster |
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| Authors: | J Price S Phillipps A Huxor N Trentham H C Ferguson R O Marzke A Hornschemeier P Goudfrooij D Hammer R B Tully K Chiboucas R J Smith D Carter D Merritt M Balcells P Erwin T H Puzia |
| Institution: | Astrophysics Group, H.H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL;Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA;Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA;Department of Physics and Astronomy, San Francisco State University, San Francisco, CA 94132, USA;NASA Goddard Space Flight Centre, Code 662, Greenbelt, MD 20771, USA;Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA;Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822, USA;Department of Physics, University of Durham, Durham DH1 3LE;Astrophysics Research Institute, Liverpool John Moores University, Twelve Quays House, Egerton Wharf, Birkenhead CH41 1LD;Department of Physics, Rochester Institute of Technology, 85 Lomb Memorial Drive, Rochester, NY 14623, USA;Instituto de Astrofísica de Canarias, C/Vía Lactea s/n, 38200 La Laguna, Tenerife, Spain;Max-Planck-Institute for Extraterrestrial Physics, Giessenbachstrasse, 85748 Garching, Germany;Universitätssternwarte, Scheinerstrasse 1, 81679 München, Germany;Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria, BC V9E 2E7, Canada |
| Abstract: | The Hubble Space Telescope /Advanced Camera for Surveys ( HST /ACS) Coma Cluster Treasury Survey is a deep two-passband imaging survey of the nearest very rich cluster of galaxies, covering a range of galaxy density environments. The imaging is complemented by a recent wide field redshift survey of the cluster conducted with Hectospec on the 6.5-m Monolithic Mirror Telescope (MMT). Among the many scientific applications for these data is the search for compact galaxies. In this paper, we present the discovery of seven compact (but quite luminous) stellar systems, ranging from M32-like galaxies down to ultra-compact dwarfs (UCDs)/dwarf to globular transition objects (DGTOs). We find that all seven compact galaxies require a two-component fit to their light profile and have measured velocity dispersions that exceed those expected for typical early-type galaxies at their luminosity. From our structural parameter analysis, we conclude that three of the samples should be classified as compact ellipticals or M32-like galaxies, and the remaining four being less extreme systems. The three compact ellipticals are all found to have old luminosity weighted ages (?12 Gyr), intermediate metallicities (?0.6 < Fe/H] < ?0.1) and high Mg/Fe] (?0.25). Our findings support a tidal stripping scenario as the formation mode of compact galaxies covering the luminosity range studied here. We speculate that at least two early-type morphologies may serve as the progenitor of compact galaxies in clusters. |
| Keywords: | surveys galaxies: clusters: individual: Coma galaxies: dwarf galaxies: structure |