Chemical evolution of the galactic bulge as derived from high-resolution infrared spectroscopy of K and M red giants

Katia Cunha, Verne V. Smith

Research output: Contribution to journalArticlepeer-review

83 Scopus citations

Abstract

We present chemical abundances in K and M red giant members of the Galactic bulge derived from high-resolution infrared spectra obtained with the Phoenix spectrograph on Gemini-South. The elements studied are carbon, nitrogen, oxygen, sodium, titanium, and iron. The evolution of C and N abundances in the studied red giants shows that their oxygen abundances represent the original values with which the stars were born. Oxygen is a superior element for probing the timescale of bulge chemical enrichment via [O/Fe] versus [Fe/H]. 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. Titanium also behaves similarly to oxygen with respect to iron. Based on these elevated values of [O/Fe] and [Ti/Fe] extending to large Fe abundances, it is suggested that the bulge underwent a more rapid chemical enrichment than the halo. In addition, there are declines in both [O/Fe] and [Ti/Fe] in those bulge targets with the largest Fe abundances, signifying another source affecting chemical evolution: perhaps supernovae of Type Ia. Sodium abundances increase dramatically in the bulge with increasing metallicity, possibly reflecting the metallicity-dependent yields from supernovae of Type II, although Na contamination from H-burning in intermediate-mass stars cannot be ruled out.

Original languageEnglish (US)
Pages (from-to)491-501
Number of pages11
JournalAstrophysical Journal
Volume651
Issue number1 I
DOIs
StatePublished - Nov 1 2006
Externally publishedYes

Keywords

  • Nuclear reactions, nucleosynthesis, abundances
  • Stars: abundances

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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