Abundance Ratios in the Galactic Bulge and Super Metal-Rich Type II Nucle osynthesis

Abstract

We present abundance results from our Keck/HIRES observations of giants in the Galactic Bulge. We confirm that the metallicity distribution of giants in the low-reddening bulge field Baade's Window can be well-fit by a closed-box enrichment model. We also confirm previous observations that find enhanced [Mg/Fe], [Si/Fe] and [Ca/Fe] for all bulge giants, including those at super-solar metallicities. However, we find that the [O/Fe] ratios of metal-rich bulge dwarfs decrease with increasing metallicity, contrary to what is expected if the enhancements of the other $α$-elements is due to Type II supernovae enrichment. We suggest that the decrease in oxygen production may be due to mass loss in the pre-supernova evolution of metal-rich progenitors.

Conference proceeding to Nuclei in the Cosmos VIII, Vancouver, BC, July, 2004. Based on data obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial support of the W. M. Keck Foundation