AAS Meeting #193 - Austin, Texas, January 1999
Session 8. Galactic Morphology and Stellar Populations
Display, Wednesday, January 6, 1999, 9:20am-6:30pm, Exhibit Hall 1

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[8.01] The Large-Scale Distribution of Stars in the Ursa Minor Dwarf Spheroidal

C. J. Grillmair (SIRTF Science Center), M. Irwin (Institute of Astronomy)

We examine the large-scale distribution of stars surrounding the dwarf spheroidal galaxy in Ursa Minor. We use APM scans of three POSSII fields to obtain photographic BJ and R magnitudes for stars over a 75 square degree area. By selecting only those stars with colors and magnitudes consistent with Umi itself, we eliminate the majority of foreground stars from the analysis. Mapping the remaining stars (primarily those on the horizontal branch) we find some evidence for surface density enhancements on large scales which we associate with tidal tails. We are limited primarily by the depth of the sky-limited plate material; upcoming wide-field CCD imaging campaigns will enable significant improvements in this area.


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