The Chemical Evolution of the Galactic Halo
Abstract
Recent determinations of [Fe/H] for individual stars in globular clusters are used to obtain the frequency function in [Fe/H] among 60 halo globular clusters. The shape of this distribution is unlike its counterpart in the solar vicinity in that there are relatively more very metal-poor stars in the halo. The halo distribution is compared with that predicted by Larson's hydrodynamical models for elliptical galaxies, and it is found that star formation is less efficient in the galactic halo than in the outer regions of the models. A satisfactory fit to the observations is obtained by making either of two modifications to a simple one-zone model. The first assumes a decrease in the heavy-element yield by a factor of 13 and results in a model with a very large halo mass/disk mass ratio. Alternatively, if gas is temporarily removed from the halo star-forming region and eventually forms a disk, the resulting ratio of halo mass to disk mass becomes 8 percent, and the G-dwarf problem in the solar neighborhood is slightly alleviated. Subject headings: clusters: globular - galaxies: stellar content - stars: abundances - stars: evolution
- Publication:
-
The Astrophysical Journal
- Pub Date:
- October 1976
- DOI:
- 10.1086/154735
- Bibcode:
- 1976ApJ...209..418H