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Chemical Evolution of the Galactic Bulge as Derived from High‐Resolution Infrared Spectroscopy of K and M Red Giants
Author(s) -
Kátia Cunha,
Verne V. Smith
Publication year - 2006
Publication title -
the astrophysical journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.376
H-Index - 489
eISSN - 1538-4357
pISSN - 0004-637X
DOI - 10.1086/507673
Subject(s) - bulge , astrophysics , metallicity , stars , oxygen , physics , supernova , chemistry , quantum mechanics
We present chemical abundances in K and M red-giant members of the Galacticbulge derived from high-resolution infrared spectra obtained with the Phoenixspectrograph on Gemini-South. The elements studied are carbon, nitrogen,oxygen, sodium, titanium, and iron. The evolution of C and N abundances in thestudied red-giants show that their oxygen abundances represent the originalvalues with which the stars were born. Oxygen is a superior element for probingthe 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 similarlyto 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 bulgeunderwent a more rapid chemical enrichment than the halo. In addition, thereare declines in both [O/Fe] and [Ti/Fe] in those bulge targets with the largestFe abundances, signifying another source affecting chemical evolution: perhapsSupernovae of Type Ia. Sodium abundances increase dramatically in the bulgewith increasing metallicity, possibly reflecting the metallicity dependantyields from supernovae of Type II, although Na contamination from H-burning inintermediate mass stars cannot be ruled out.Comment: ApJ in pres

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