Detailed Abundances in the Galactic Center: Evidence of a Metal-rich Alpha-enhanced Stellar Population
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 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.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- May 2020
- DOI:
- 10.3847/1538-4357/ab8226
- arXiv:
- arXiv:2003.11085
- Bibcode:
- 2020ApJ...894...26T
- Keywords:
-
- Chemical abundances;
- Late-type stars;
- Star clusters;
- Galactic center;
- Galaxy chemical evolution;
- Chemical enrichment;
- 224;
- 909;
- 1567;
- 565;
- 580;
- 225;
- Astrophysics - Astrophysics of Galaxies;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 13 pages, 10 figures, accepted for publication in ApJ, Figure 7 corrected