Volume 430, Number 2, February I 2005
|Page(s)||L25 - L28|
|Published online||20 January 2005|
Letter to the Editor
Discovery of two M 32 twins in Abell 1689*
Sternwarte der Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany e-mail: firstname.lastname@example.org
2 Departamento de Astronomía y Astrofísica, Pontificia Universidad Católica de Chile, Casilla 306, Santiago 22, Chile
3 Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA
4 Instituto de Astrofísica de Andalucía (CSIC), Camino Bajo de Huétor 24, Granada 18008, Spain
Accepted: 9 December 2004
The M 31 satellite galaxy M 32 has long been considered an object of unique properties, being the most extreme example of the very rare compact elliptical galaxy class. Here we present the spectroscopic discovery of two M 32 twins in the massive galaxy cluster Abell 1689. As these objects are so rare, this is an important step towards a better understanding of the nature of compact galaxies. The two M 32 twins had first been detected within our photometric search for ultra compact dwarf galaxy (UCDs) candidates in A1689 (Mieske et al. [CITE], AJ, 128, 1529) with the Advanced Camera for Surveys (ACS). Their luminosities ( mag) are very similar to M 32 and their surface brightness profiles are consistent with that of M 32 projected to A1689's distance. From our ACS imaging we detect several fainter compact galaxy candidates with luminosities intermediate between M 32 and the Fornax UCDs. If spectroscopically confirmed as cluster members, this would almost close the gap in the mag-μ plane between the region of UCDs and the compact ellipticals, implying a sequence of faint compact galaxies well separated from that of dwarf ellipticals.
Key words: galaxies: clusters: individual: Abell 1689 / galaxies: dwarf / galaxies: structure / galaxies: interactions
© ESO, 2005
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