Katia Cunha (1, 2), Verne Smith (1), Kris Sellgren (3), Robert Blum (1, 5), Solange Ramirez (4), and Donald M. Terndrup (3)
to appear in Formation and Evolution of Galaxy Bulges, Proceedings IAU Symposium No. 245, 2007, M. Bureau et al. eds., in press (arXiv:0710.0866)
We discuss oxygen and iron abundance patterns in K and M red-giant members of the Galactic bulge and in the young and massive M-type stars inhabiting the very center of the Milky Way. The abundance results from the different bulge studies in the literature, both in the optical and the infrared, indicate that the [O/Fe]-[Fe/H] relation in the bulge does not follow the disk relation, with [O/Fe] values falling above those of the disk. Based on these elevated values of [O/Fe] extending to large Fe abundances, it is suggested that the bulge underwent a rapid chemical enrichment with perhaps a top-heavy initial mass function. The Galactic Center stars reveal a nearly uniform and slightly elevated (relative to solar) iron abundance for a studied sample which is composed of 10 red giants and supergiants. Perhaps of more significance is the fact that the young Galactic Center M-type stars show abundance patterns that are reminiscent of those observed for the bulge population and contain enhanced abundance ratios of alpha-elements relative to either the Sun or Milky Way disk at near-solar metallicities.
(1) National Optical Astronomy Observatory
(2) on leave from Observatorio Nacional, Rio de Janeiro, Brazil
(3) Ohio State University
(4) Infrared Processing and Analysis Center, Caltech
(5) Based on observations obtained at the Gemini Observatory,
which is operated by the Association
of Universities for Research in Astronomy, Inc., under a cooperative
agreement with the NSF on behalf of the Gemini partnership.
Return to Kris Sellgren's preprint page
Return to Kris Sellgren's home page
Revised: 2007 October 5 (ks)