2007ApJ...665L.119R

We report the first abundance analysis of 17 M giant stars in the inner Galactic bulge at (l, b) = (0°, -1°), based on R=25,000 infrared spectroscopy (1.5-1.8 µm) using NIRSPEC at the Keck telescope. Based on their luminosities and radial velocities, we identify these stars with a stellar population older than 1 Gyr. We find the iron abundance <[Fe/H]≥-0.22±0.03, with a 1 σ dispersion of 0.14±0.024. We also find the bulge stars have an enhanced [α/Fe] abundance ratio at the level of +0.3 dex relative to solar stars, and low <¹²C/¹³C> ~ 6.5±0.3. The derived iron abundance and composition for this inner bulge sample is indistinguishable from that of a sample of M giants our team has previously studied in Baade's window (l, b) = (0.9, -4). We find no evidence of any major iron abundance or abundance ratio gradient between this inner field and Baade's window.