AAS 207th Meeting, 8-12 January 2006
Session 133 The Milky Way
Poster, Wednesday, 9:20am-6:30pm, January 11, 2006, Exhibit Hall

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[133.08] Dissecting the Milky Way with SDSS - I: Stellar Overdensities

R. H. Lupton, M. Juric (Princeton U.), Z. Ivezic, A. Brooks (U. Washington), D. J. Schlegel (LBL), D. Finkbeiner, N. Padmanabhan, N. Bond (Princeton U.), C. M. Rockosi (U. C. Santa Cruz), G. R. Knapp, J. E. Gunn, T. Sumi (Princeton U.), D. P. Schneider (Penn. State)

We utilize the photometric parallax method to estimate the distances to 50 million stars detected by the SDSS, and map the stellar number density distribution as a function of position in the Galaxy. The currently available data cover 6,500 square degrees of sky, and sample distances ranging from 100 pc to 15 kpc. Using smooth Galaxy models to subtract the background, we detect several known and new overdensities. Extrapolating to the whole Milky Way disk volume, we estimate that there are 20-40 such clumps scattered through the Galaxy. A remarkable new feature is seen over 1000 square degrees of sky centered at l=300, b=60, at distances 10-15 kpc. The u-g color distribution of the stars associated with this overdensity implies metallicities lower than those of the thick disk, and consistent with the halo metallicity. Despite the lack of kinematic data, these properties suggest that this overdensity may be a nearby low-surface brightness dwarf galaxy merging with the Milky Way.

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