The First Detailed Abundances for M Giants in Baade’s Window from Infrared Spectroscopy

We report the first abundance analysis of 14 M giant stars in the Galacticbulge, based on R=25,000 infrared spectroscopy (1.5-1.8um) using NIRSPEC at theKeck II telescope. Because some of the bulge M giants reach high luminositiesand have very late spectral type, it has been suggested that they are theprogeny of only the most metal rich bulge stars, or possibly members of ayounger bulge population. We find the iron abundance and composition of the Mgiants are similar to those of the K giants that have abundances determinedfrom optical high resolution spectroscopy: <[Fe/H]>=-0.190 +/- 0.020 with a1-sigma dispersion of 0.08 +/- 0.015. Comparing our bulge M giants to a controlsample of local disk M giants in the Solar vicinity, we find the bulge starsare enhanced in alpha elements at the level of +0.3 dex relative to the Solarcomposition stars, consistent with other studies of bulge globular clusters andfield stars. This small sample shows no dependence of spectral type onmetallicity, nor is there any indication that the M giants are the evolvedmembers of a subset of the bulge population endowed with specialcharacteristics such as relative youth or high metallicity. We also find low12C/13C < 10, confirming the prsence of extra-mixing processes during the redgaint phase of evolutionComment: 19 pages, 7 figures, accepted for publication in the Astrophysical Journa