Investigate Substructures of the Inner Halo Using the StarGO Algorithm with APOGEE DR17
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| Format: | Preprint |
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2025
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| _version_ | 1866909561391153152 |
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| author | Li, Zhongcheng Du, Cuihua Liu, Haoyang Ye, Dashuang |
| author_facet | Li, Zhongcheng Du, Cuihua Liu, Haoyang Ye, Dashuang |
| contents | We applied Stars' Galactic Origin (StarGO) algorithm in 7D space (i.e., [Fe/H], [Mg/Fe], [Al/Fe], $L_{z}$, $J_{r}$, $J_{z}$, $E$) to analyze stars in the inner halo with APOGEE DR17. We identified some known substructures, including Gaia-Sausage-Enceladus (GSE), Sagittarius Stream (Sgr), LMS-1 (Wukong), Thamnos, Metal-Weak Thick Disk (MWTD) and Aleph. Additionally, we identified an undefined metal-poor group (UDG, with [Fe/H] $<-0.8$ dex) probably linked to known substructure like Aleph, as well as a high $α$-abundance substructure (HAS) associated with both the Nyx and Nyx-2 streams. Chemical abundance of the HAS supports the argument that Nyx and Nyx-2 share a common origin. We discovered three substructures, which we refer to as new-substructure candidate-1,2,3 (NSTC-1,2,3). Despite exhibiting disk-like dynamics, these NSTCs demonstrate notably low [Mg/Fe] ($<$ 0.2 dex) and [Al/Fe] ($<$ $-0.15$ dex), similar to the properties of dwarf galaxies. Their high orbital energy and low [$α$/Fe] indicate the association with recent accretion events. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2504_01536 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Investigate Substructures of the Inner Halo Using the StarGO Algorithm with APOGEE DR17 Li, Zhongcheng Du, Cuihua Liu, Haoyang Ye, Dashuang Astrophysics of Galaxies We applied Stars' Galactic Origin (StarGO) algorithm in 7D space (i.e., [Fe/H], [Mg/Fe], [Al/Fe], $L_{z}$, $J_{r}$, $J_{z}$, $E$) to analyze stars in the inner halo with APOGEE DR17. We identified some known substructures, including Gaia-Sausage-Enceladus (GSE), Sagittarius Stream (Sgr), LMS-1 (Wukong), Thamnos, Metal-Weak Thick Disk (MWTD) and Aleph. Additionally, we identified an undefined metal-poor group (UDG, with [Fe/H] $<-0.8$ dex) probably linked to known substructure like Aleph, as well as a high $α$-abundance substructure (HAS) associated with both the Nyx and Nyx-2 streams. Chemical abundance of the HAS supports the argument that Nyx and Nyx-2 share a common origin. We discovered three substructures, which we refer to as new-substructure candidate-1,2,3 (NSTC-1,2,3). Despite exhibiting disk-like dynamics, these NSTCs demonstrate notably low [Mg/Fe] ($<$ 0.2 dex) and [Al/Fe] ($<$ $-0.15$ dex), similar to the properties of dwarf galaxies. Their high orbital energy and low [$α$/Fe] indicate the association with recent accretion events. |
| title | Investigate Substructures of the Inner Halo Using the StarGO Algorithm with APOGEE DR17 |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2504.01536 |