Detailed Abundances in the Galactic Center : Evidence of a Metal-rich Alpha-enhanced Stellar Population

Summary, in English

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 spectrograph 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 α-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 compositions.

• Author: 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
• Department/s: Lund Observatory - Has been reorganised
• Publishing year: 2020
• Language: English
• Publication/Series: Astrophysical Journal
• Volume: 894
• Issue: 1
• Links: http://dx.doi.org/10.3847/1538-4357/ab8226
• Document type: Journal article
• Publisher: American Astronomical Society
• Topic: Astronomy, Astrophysics and Cosmology
• Status: Published
• ISBN/ISSN/Other: ISSN: 0004-637X