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arXiv · 2003.11085

Detailed abundances in the Galactic center: Evidence of a metal-rich alpha-enhanced stellar population

B. Thorsbro·N. Ryde·R. M. Rich·M. Schultheis·F. Renaud·E. Spitoni·T. K. Fritz·A. Mastrobuono-Battisti·L. Origlia·F. Matteucci·R. Schödel
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Abstract

We present a detailed study of the composition of 20 M giants in the Galactic center with 15 of them confirmed to be in the Nuclear Star Cluster. As a control sample we have also observed 7 M giants in the Milky Way Disk with similar stellar parameters. All 27 stars are observed using the NIRSPEC spectograph on the KECK II telescope in the K-band at a resolving power of R=23,000. We report the first silicon abundance trends versus [Fe/H] for stars in the Galactic center. While finding a disk/bulge like trend at subsolar metallicities, we find that [Si/Fe] is enhanced at supersolar metallicities. We speculate on possible enrichment scenarios to explain such a trend. However, the sample size is modest and the result needs to be confirmed by additional measurements of silicon and other \textalpha-elements. We also derive a new distribution of [Fe/H] and find the most metal rich stars at [Fe/H]=+0.5 dex, confirming our earlier conclusions that the Galactic center hosts no stars with extreme chemical composition.

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B. Thorsbro, N. Ryde, R. M. Rich, M. Schultheis, F. Renaud, E. Spitoni, T. K. Fritz, A. Mastrobuono-Battisti, L. Origlia, F. Matteucci, R. Schödel. 2020-03-26. Detailed abundances in the Galactic center: Evidence of a metal-rich alpha-enhanced stellar population. https://doi.org/10.3847/1538-4357%2Fab8226

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