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| Paper: |
The Composition and Stellar Populations of M5 |
| Volume: |
92, Formation of the Galactic Halo. . . . Inside and Out |
| Page: |
293 |
| Authors: |
Sandquist, E.; Bolte, M.; Stetson, P. |
| Abstract: |
We present the results of BVI photometry of nearly 30,000 stars in the globular cluster M5. With large samples of stars in nearly every phase of stellar evolution, we have been able to make detailed comparisons between M5's color-magnitude diagram (CMD) and luminosity function (LF), and the predictions of evolutionary theory. \newline The R method of calculating helium content returns a value of Y = 0.20 +/- 0.02. \newline The relative numbers of stars on the red-giant branch (RGB) and main sequence (MS) agree well with canonical LFs (which is not the case for the most metal-poor clusters). \newline Even with very restrictive cuts in the CMD around the fiducial line of the cluster, the blending of stellar images will enhance the number of stars observed to be just above the turnoff, and at the very base of the RGB. This effect is likely to be responsible for ``subgiant excesses'' observed in metal-poor clusters. \newline alpha -element enhancement can explain the majority of the discrepancy between the observed and predicted positions of the red giant bump, which reduces the need for convective overshooting, but does not eliminate it. |
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