تقرير
High-Resolution Chemical Abundances of the Nyx Stream
| العنوان: | High-Resolution Chemical Abundances of the Nyx Stream |
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| المؤلفون: | Wang, Shuyu, Necib, Lina, Ji, Alexander P., Ou, Xiaowei, Lisanti, Mariangela, Reyes, Mithi A. C. de los, Strom, Allison L., Truong, Mimi |
| المصدر: | ApJ 955 (2023) 2 |
| سنة النشر: | 2022 |
| المجموعة: | Astrophysics |
| مصطلحات موضوعية: | Astrophysics - Astrophysics of Galaxies |
| الوصف: | Nyx is a nearby, prograde, and high-eccentricity stellar stream physically contained in the thick disk but with an unknown origin. Nyx could be the remnant of a disrupted dwarf galaxy, in which case the associated dark matter substructure could affect terrestrial dark matter direct detection experiments. Alternatively, Nyx could be a signature of the Milky Way's disk formation and evolution. To determine the origin of Nyx, we obtained high-resolution spectroscopy of 34 Nyx stars using Keck/HIRES and Magellan/MIKE. A differential chemical abundance analysis shows that most Nyx stars reside in a metal-rich ($\mbox{[Fe/H]} > -1$) high-$\alpha$ component that is chemically indistinguishable from the thick disk. This rules out an originally suggested scenario that Nyx is the remnant of a single massive dwarf galaxy merger. However, we also identify five substantially more metal-poor stars ($\mbox{[Fe/H]} \sim -2.0$) that have chemical abundances similar to the metal-weak thick disk. It remains unclear how stars chemically identical to the thick disk can be on such prograde, high-eccentricity orbits. We suggest two most likely scenarios: that Nyx is the result of an early minor dwarf galaxy merger or that it is a record of the early spin-up of the Milky Way disk -- although neither perfectly reproduces the chemodynamic observations. The most likely formation scenarios suggest that future spectroscopic surveys should find Nyx-like structures outside of the Solar Neighborhood. Comment: 25 pages, 6 figures, Appendix by Shuyu Wang, accepted by the Astrophysical Journal on July 29, 2023 |
| نوع الوثيقة: | Working Paper |
| DOI: | 10.3847/1538-4357/acec4d |
| URL الوصول: | http://arxiv.org/abs/2210.15013 |
| رقم الأكسشن: | edsarx.2210.15013 |
| قاعدة البيانات: | arXiv |
| DOI: | 10.3847/1538-4357/acec4d |
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