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| Main Authors: | , , , |
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| Format: | Preprint |
| Published: |
2024
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2412.06187 |
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Table of Contents:
- We explore the metal-poor regime of the Galactic disk on the distribution of stars in the [$α$/M]-$V_ϕ$ plane, to identify the most metal-poor thin disk (MPTnD) stars belonging to the low-$α$ sequence. Chemical abundances and velocities of sample stars are either taken or derived from APOGEE DR17 and Gaia DR3 catalogs. We find the existence of a well-separated extension of the kinematically thin disk stars in the metallicity range of -1.2 $<$[M/H]$<$ -0.8 dex. Based on two-by-two distributions of [Mg/Mn], [Al/Fe] and [C+N/Fe], we further confirmed 56 high-possibility metal-poor thin disk (HP-MPTnD) giant stars and suggested the lower metallicity limit of the thin disk below -0.95 dex. A comparative analysis of HP-MPTnD sample with other Galactic components revealed its chemo-dynamical similarities with canonical thin disk stars. These low-$α$ metal-poor stars are predominantly located in the outer disk region and formed in the early stage of the formation of thin disk. Their existence provides compelling support for the two-infall model of the Milky way's disk formation. Moreover, these stars impose observational constraints on the timing and metallicity of the second gas infall event.