Collaborative Research: Fundamental Properties of Local Subdwarfs

AST-0205815啤酒，蒂莫西·C·D。Beers在密歇根州立大学获得资金，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我们的银河系是如何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恒星的运动和化学丰度的理解，这些恒星的重元素含量远远低于普通恒星，以及这些恒星与球状星团恒星的比较情况。这些“亚矮星”的已知样本非常少。比尔斯和合作者将在银河系的光环和厚圆盘中研究这些亚矮星的新样本；这个样本比之前研究的亚矮星数量有了巨大的增加。研究人员将获得对温度、变红和成分的准确和自洽的测量，这些测量是在最近对贫金属星的调查中精心挑选的大约150颗亚矮星的样本。他们还将应用理论模型来探索主序光度与恒星详细化学成分的相关性。这些结果将用于改进球状星系团主要序列的温度和丰度尺度，以便与巨型分支上的光谱测定进行比较，从而确定球状星系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.