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J.R. Hargis, E.L. Sandquist (San Diego State University), M. Bolte (University of California, Santa Cruz)
We present wide-field (24 arcmin x 24 arcmin) BVI photometry of the globular cluster M12 (NGC 6218 = C 1644-018). The generated V and I band luminosity functions and color-magnitude diagrams are based on this sample of nearly 20,000 stars. Extensive artificial star tests have been performed in order to examine the incompleteness as a function of cluster magnitude and radius. Because the luminosity function acts as probe of the number of stars at different evolutionary states, the relative number of stars at each point can give clues to the physics involved in their evolution. In particular, we discuss the relative numbers (on the upper main sequence, subgiant and giant branches) in order to investigate the effects of deep mixing in stellar interiors. This process, in red giant branch (RGB) stars, brings hydrogen-rich material into the base of the outer convective zone and shows up most readily in the RGB bump of the luminosity function. Furthermore, we study the possibility of a subgiant excess on the luminosity function and the presence of blue stragglers in the cluster.
The author(s) of this abstract have provided an email address for comments about the abstract: jhargis@sciences.sdsu.edu
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.