Detailed abundances in the Galactic center: Evidence of a metal-rich alpha-enhanced stellar population. (arXiv:2003.11085v1 [astro-ph.GA])

Detailed abundances in the Galactic center: Evidence of a metal-rich alpha-enhanced stellar population. (arXiv:2003.11085v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Thorsbro_B/0/1/0/all/0/1">B. Thorsbro</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ryde_N/0/1/0/all/0/1">N. Ryde</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rich_R/0/1/0/all/0/1">R. M. Rich</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schultheis_M/0/1/0/all/0/1">M. Schultheis</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Renaud_F/0/1/0/all/0/1">F. Renaud</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Spitoni_E/0/1/0/all/0/1">E. Spitoni</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fritz_T/0/1/0/all/0/1">T. K. Fritz</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mastrobuono_Battisti_A/0/1/0/all/0/1">A. Mastrobuono-Battisti</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Origlia_L/0/1/0/all/0/1">L. Origlia</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Matteucci_F/0/1/0/all/0/1">F. Matteucci</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schodel_R/0/1/0/all/0/1">R. Sch&#xf6;del</a>

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.

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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