Detailed Abundances for the Old Population near the Galactic Center: I. Metallicity distribution of the Nuclear Star Cluster

TL;DR

This study provides the first high-resolution spectroscopic analysis of old stars near the Galactic Center, revealing their metallicity distribution and suggesting similarities with the Galactic bulge rather than the disk or halo.

Contribution

It presents new high-resolution infrared spectra of stars near the Galactic Center, offering detailed metallicity measurements and distribution analysis.

Findings

Median metallicity of -0.16 with a large spread

Most stars have metallicities at or below Solar

Metallicity distribution resembles that of the Galactic bulge

Abstract

We report the first high spectral resolution study of 17 M giants kinematically confirmed to lie within a few parsecs of the Galactic Center, using R=24,000 spectroscopy from Keck/NIRSPEC and a new linelist for the infrared K band. We consider their luminosities and kinematics, which classify these stars as members of the older stellar population and the central cluster. We find a median metallicity of <[Fe/H]>=-0.16 and a large spread from approximately -0.3 to +0.3 (quartiles). We find that the highest metallicities are [Fe/H]<+0.6, with most of the stars being at or below the Solar iron abundance. The abundances and the abundance distribution strongly resembles that of the Galactic bulge rather than disk or halo; in our small sample we find no statistical evidence for a dependence of velocity dispersion on metallicity.