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| Paper: |
The Age Structure of the Halo |
| Volume: |
165, The Third Stromlo Symposium: The Galactic Halo |
| Page: |
46 |
| Authors: |
Vandenberg, Don A. |
| Abstract: |
On the basis of new stellar evolutionary models that treat the observed enhancements in the alpha-elements explicitly, the ages of globular clusters and field stars in the Galactic halo are determined. Indications are that field and cluster stars are coeval, that 14 Gyr is the current best estimate of the age of the most metal-deficient stars, and that there is an appreciable age--metallicity relation in the halo: systems having [Fe/H] near -1 appear to be ~2 Gyr younger than those having [Fe/H] <= -2. The dispersion in age at a fixed metallicity, especially at the lowest [Fe/H]'s, is small --- too small for age to be the second parameter. There may be some (slight) dependence of age on Galactocentric distance (R_G) and the dispersion in age at large R_G may be somewhat larger than that at small R_G. |
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