We will use the unique imaging capabilities of the refurbished HST and the WFPC2 to determine mass and luminosity functions for the lowest-luminosity stars in one of the nearest Galactic globular clusters, M4. Our deep U, V, and I images will allow us to probe two low-luminosity populations: the low-mass main-sequence stars, and the white dwarfs. Understanding the contribution that these stars make to the overall mass budget of globular clusters will provide new understanding of dynamical evolution, star formation in the early universe, the dark-matter content of the halo of our Galaxy, and the evolution of white dwarfs. Our color-magnitude diagrams will yield for the first time cooling sequences for hot white dwarfs in globular clusters, direct observations of the binary populations in the cluster cores, and the turndown of the Population II main sequence where the ZAMS merges with the Hayashi track for convective stars. Major support programs being carried out by our team members in association with this proposal include theoretical modeling of the evolution of low-mass stars, model atmospheres and the transformation of the theoretical spectra of these stars to HST colors, and the development of photometric algorithms optimized for HST data.
- Pub Date:
- January 1994