AAS 201st Meeting, January, 2003
Session 50. The Milky Way: From Center to Halo
Poster, Tuesday, January 7, 2003, 9:20am-6:30pm, Exhibit Hall AB

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[50.09] A Study of the Kinematics of Stars at the North Galactic Pole

A.A. Polak, S.R. Majewski, J.D. Crane, J.C. Ostheimer, H.J. Rocha-Pinto, R.J. Patterson (University of Virginia)

Following on the study of the kinematics of F-K stars in a deep (B~22.5) North Galactic Pole survey by Majewski (1992), we have produced a complimentary study of K-M stars in the same field. The data include deep BVI CCD photometry combined with unpublished proper motion data from Majewski's original survey. For late-type stars, the Reduced Proper Motion Diagram is a useful discriminant between dwarfs and giants, and we compute photometric parallaxes based on the appropriate luminosity class for each star. The quartiles of the distance distribution of our complete, magnitude-limited sample are 0.6, 1.4, and 3.5 kpc. U and V velocities are determined directly from the proper motions for all stars, while W velocities are known only for a subset of stars for which radial velocities have been measured. Our K-M dwarf sample is particularly useful for study of the disk populations of the Galaxy. For example, we find an asymmetric drift gradient of -38 km s-1 kpc-1 out to ~4 kpc for the disk component of our sample. In our more distant subsample, we see further evidence of a retrograde moving group in the Galactic halo which may be related to the one discerned by Majewski, Munn and Hawley (1996).

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