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

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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.