تقرير
Measuring the alpha-abundance of subsolar-metallicity stars in the Milky Way's central half-parsec: testing globular cluster and dwarf galaxy infall scenarios
| العنوان: | Measuring the alpha-abundance of subsolar-metallicity stars in the Milky Way's central half-parsec: testing globular cluster and dwarf galaxy infall scenarios |
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| المؤلفون: | Bentley, Rory O., Do, Tuan, Kerzendorf, Wolfgang, Chu, Devin S., Chen, Zhuo, Konopacky, Quinn, Ghez, Andrea |
| سنة النشر: | 2021 |
| المجموعة: | Astrophysics |
| مصطلحات موضوعية: | Astrophysics - Astrophysics of Galaxies, Astrophysics - Solar and Stellar Astrophysics |
| الوصف: | While the Milky Way Nuclear star cluster has been studied extensively, how it formed is uncertain. Studies have shown it contains a solar and supersolar metallicity population that may have formed in-situ, along with a subsolar metallicity population that may have formed via mergers of globular clusters and dwarf galaxies. Stellar abundance measurements are critical to differentiate between formation scenarios. We present new measurements of [$M/H$] and $\alpha$-element abundances [$\alpha/Fe$] of two subsolar-metallicity stars in the Galactic Center. These observations were taken with the adaptive-optics assisted high-resolution (R=24,000) spectrograph NIRSPEC in the K-band (1.8 - 2.6 micron). These are the first $\alpha$-element abundance measurements of sub-solar metallicity stars in the Milky Way nuclear star cluster. We measure [$M/H$]=$-0.59\pm 0.11$, [$\alpha/Fe$]=$0.05\pm 0.15$ and [$M/H$]= $-0.81\pm 0.12$, [$\alpha/Fe$]= $0.15\pm 0.16$ for the two stars at the Galactic center; the uncertainties are dominated by systematic uncertainties in the spectral templates. The stars have an [$\alpha/Fe$] in-between the [$\alpha/Fe$] of globular clusters and dwarf galaxies at similar [$M/H$] values. Their abundances are very different than the bulk of the stars in the nuclear star cluster. These results indicate that the sub-solar metallicity population in the Milky Way nuclear star cluster likely originated from infalling dwarf galaxies or globular clusters and are unlikely to have formed in-situ. Comment: Accepted by ApJ |
| نوع الوثيقة: | Working Paper |
| DOI: | 10.3847/1538-4357/ac3910 |
| URL الوصول: | http://arxiv.org/abs/2112.02649 |
| رقم الأكسشن: | edsarx.2112.02649 |
| قاعدة البيانات: | arXiv |
| DOI: | 10.3847/1538-4357/ac3910 |
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