Collaborative Research: Stellar Physics from Cluster-Wide Samples in Globular Clusters

圣迭戈州立大学/加州大学圣克鲁斯分校合作研究：来自全球星团的星团范围样本的恒星物理学摘要将对低质量恒星的结构和演化理论进行一系列观测测试。具体地说，球状星团恒星的计数(即光度函数)将被用来确定演化时间尺度。此外，还将测量内部一致的光度法，以比较不同星系团在不同演化阶段和相同演化点的恒星性质(光度、温度)。星系团颜色星等图的三个方面将被考察：1)红巨星分支上升的时代，包括红巨星演化时间尺度、红巨星分支凸起(其亮度和锐度)和红巨星分支尖端的位置；2)水平分支和渐近巨型分支的形态、分布和演化；以及3)蓝散星及其径向分布、聚集色等图上的分布，以及异常蓝散星群的存在。这些研究的统计性质要求对大样本星系星进行高质量的光度测量，这些样本将从以前获得的宽视场(对于星团外围)和高分辨率(对于星团核心)图像中提取，这些图像是由国家和国际天文台望远镜获得的(以及尽可能包括哈勃空间望远镜在内的档案图像)。圣地亚哥大学的本科生和硕士研究生将大量参与这项工作--包括天文数据的减少和分析，以及先进统计方法的应用。加州大学圣迭戈分校的研究生培训也得到了支持。最终的测光也将公之于众。

AST-0507785 / AST-0507697Eric Sandquist / Michael BolteSan Diego State University / University of California Santa CruzCollaborative Research: Stellar Physics from Cluster-Wide Samples in GlobularStar ClustersABSTRACTA series of observational tests of theories of the structure and evolution of low mass stars will beperformed. Specifically, counts of globular cluster stars (i.e., luminosity functions) will beemployed to determine evolutionary timescales. Also, internally-consistent photometry will bemeasured to compare stellar properties (luminosity, temperature) at different phases of evolutionand at the same points of evolution across different clusters. Three aspects of the cluster colormagnitudediagrams will be examined: 1) The epoch of red giant branch ascent, including red giantevolutionary timescales, the red giant branch bump (its luminosity and sharpness), and thelocation of the red giant branch-tip; 2) horizontal branch and asymptotic giant branch morphologies,distributions, and evolution; and 3) blue stragglers and their radial distributions, distributions on thecluster color magnitude diagrams, and the presence of unusual blue straggler populations. Thestatistical nature of these investigations requires quality photometry of large samples of cluster starswhich will be extracted from previously obtained wide field (for cluster outskirts) and highresolution (for cluster cores) images obtained at national and international observatories telescopes(plus archival images, including the Hubble Space Telescope where possible). Novel (within theastronomical community) statistics will also be employed in the analysis to assesssignificance/confidence levels of trends and relations.Undergraduate and Master's students at San Diego will be heavily involved in this work - both withthe reduction and analysis of the astronomical data and the application of advanced statisticalmethods. The training of a graduate student at UCSC is also supported here. The final photometrywill also be made publicly available.