NOAO >   Observing Info >   Approved Programs >   2004B-0210

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Proposal Information for 2004B-0210


PI: Sebastien Lepine, American Museum of Natural History, lepine@amnh.org
Address: Department of Astrophysics, CPW at 79th street, New York, NY 10024, USA

CoI: Michael M. Shara, American Museum of Natural History
CoI: R. Michael Rich, U.C.L.A.

Title: A search for nearby, very low-mass, ultra-cool halo subdwarfs

Abstract: The Galactic halo is expected to host a vast population of very low- mass, metal-poor stars, remnants of the first ages of star formation. While these "ultra-cool subdwarfs" should exist in large numbers, very few of them have actually been identified in the vicinity of the Sun: only a dozen subdwarfs with spectral type sdM6.0/esdM6.0 or later are currently known. As a result, the physical properties and local distribution of metal-poor stars at the bottom of the main sequence are very poorly constrained. As a by-product of our all-sky survey for faint stars with large proper motions, we have recently succeeded in identifying several hundred new candidate ultra-cool subdwarfs, some of which have been spectroscopically confirmed in a previous KPNO observing run. We propose to obtain spectra for all our candidates stars in order to confirm their subdwarf status and build a complete, well-populated spectroscopic sequence of subdwarf stars down to the hydrogen-burning limit. Using our confirmed objects and their radial velocities, we will also determine the local density of ultra-cool subdwarfs and constrain their density and distribution in the Galactic halo.


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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