Collaborative Research: Fundamental Properties of Local Subdwarfs

AST-0205815 Beers, Timothy c .博士；比尔斯获得了密歇根州立大学的资助，与德克萨斯大学奥斯汀分校和俄亥俄州立大学的合作者合作。这个团队将为更详细地了解银河系的形成和演化奠定基础。星系形成和演化的模型取决于对本地主序星的运动和化学富集的理解，这些恒星的重元素含量远低于普通恒星，以及这些恒星与球状星团恒星的比较。已知的这些“亚矮星”样本非常小。比尔斯和他的合作者将研究银河系的光环和厚盘中这些亚矮星的新样本；这个样本比以前研究过的亚矮星数量有了很大的增加。研究人员将获得精确的、自一致的温度、变红和组成的测量数据，这些数据是经过严格挑选的大约150个亚矮星样本，这些样本是在最近的贫金属恒星调查中发现的。他们还将应用理论模型来探索主序层亮度与详细的恒星化学成分的依赖关系。这些结果将用于改进球状星团主序列的温度和丰度尺度，以便与巨支的光谱测定结果进行比较，从而确定球状星团的相对年龄和距离。

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 theGalaxy'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.