Collaborative Research: Fundamental Properties of Local Subdwarfs

Michigan State University, East Lansing MI

Investigators

Abstract

AST-0205815 Beers, Timothy C. Dr. Beers is awarded funds at Michigan State University to work with collaborators at the University of Texas at Austin and Ohio State University. This team will lay the groundwork for a more detailed understanding of how our Milky Way galaxy formed and evolved. Models of galaxy formation and evolution depend on understanding the motions and chemical enrichment of local main-sequence stars that are far lower in heavy elements than ordinary stars, and how these stars compare to globular cluster stars. The known sample of these "subdwarfs" is very small. Dr. Beers and collaborators will study a new sample of these subdwarf stars in the Galaxy's halo and thick disk; this sample represents a huge increase over the number of subdwarfs previously studied. The investigators will obtain accurate and self-consistent measures of temperature, reddening, and composition for a critically selected sample of approximately 150 subdwarfs identified in recent surveys for metal-poor stars. They will also apply theoretical models to explore the dependence of the main-sequence luminosity on detailed stellar chemical composition. The results will be used to improve the temperature and abundance scales of globular cluster main sequences for comparison to spectroscopic determinations on the giant branch, and to thus determine the relative ages and distances of globular clusters.