The discovery of two extremely low luminosity Milky Way GCs


[0706.0019] The discovery of two extremely low luminosity Milky Way globular clusters:

Authors: S. Koposov (1,2), J. T. A. de Jong (1), V. Belokurov (2), H.-W. Rix (1), D.B. Zucker (2), N.W. Evans (2), G. Gilmore (2), M.J. Irwin (2), E. F. Bell (1) ((1) Max Planck Institute for Astronomy, (2) Institute of Astronomy, University of Cambridge)

(Submitted on 31 May 2007)

We report the discovery of two extremely low luminosity globular clusters in the Milky Way Halo. These objects were detected in the Sloan Digital Sky Survey Data Release 5 and confirmed with deeper imaging at the Calar Alto Observatory. The clusters, Koposov 1 and Koposov 2, are located at about 40-50 kpc and appear to have old stellar populations and luminosities of only Mv around -1. Their observed sizes of about 3 pc are well within the expected tidal limit of about 10 pc at that distance. Together with Palomar 1, AM 4 and Whiting 1, these new clusters are the lowest luminosity globulars orbiting the Milky Way (…)

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