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Proposal Information for 2002A-0302


PI: Jeffrey D. Crane, University of Virginia, jdc2k@astsun.astro.virginia.edu
Address: P.O. Box 3818, Charlottesville, VA 22903-0818, USA

CoI: Steven R. Majewski, University of Virginia
CoI: John N. Bahcall, Institute for Advanced Study
CoI: Richard J. Patterson, University of Virginia

Title: Measuring Local Dark Matter with K giants at the North Galactic Pole

Abstract: Local dark matter can be studied by measuring dynamically the local Galactic disk volume density (the ``Oort limit'' and comparing it to the volume density one gets by adding up local visible mass components. This is typically done by measuring the density and dynamics of a sample of ``tracer'' stars toward the Galactic poles. Using a variety of tracers and techniques, many such studies have been done, but with disparate results suggesting everything from no dark matter in the disk to more dark than visible matter. The construction of a large, uniform, and systematically well-measured tracer sample is a crucial part of this method. We have used Washington + DDO photometry to select a large sample of subsolar metallicity K giants at the North Galactic Pole. This proposal concerns the collection of spectroscopic data to refine our sample to the best possible homogeneity to minimize distance errors and to determine radial velocities. Once complete, this study should provide the largest and most reliable sample of dynamical ``Oort limit'' tracers yet assembled. As a result, we expect to place the strongest constraints yet on the density and scale height of dark matter in the disk. In the future, this same sample will be used in a \it Space Interferometry Mission Key Project study of the Oort limit which will refine our ground-based result by supplying transverse motions that can be incorporated into a 3-dimensional analysis of the potential and account for off-diagonal elements of the velocity correlation tensor, as well as provide extremely good trigonometric parallaxes.


National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360



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