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arXiv · 2102.05999

High-{\alpha}-Metal-Rich stars in the LAMOST-MRS survey and its connection with the galactic bulge

Haopeng Zhang·Yuqin Chen·Gang Zhao·Jingkun Zhao·Xilong Liang·Haining Li·Yaqian Wu·Ali Luo·Rui Wang
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Abstract

We report the detection of a large sample of high-$\alpha$-metal-rich stars on the low giant branch with $2.6 0.2$ than the comparison group. These properties strongly indicate its connection with the outer bar/bulge region at $R=3-5$ kpc. A tentative interpretation of this special group is that its stars were formed in the X-shaped bar/bulge region, close to its corotation radius, where radial migration is the most intense, and brings them to present locations at 9 kpc and beyond. Low eccentricities and slightly outward radial excursions of its stars are consistent with this scenario. Its kinematics (cold) and chemistry ($[\alpha/Fe]$ $\sim 0.1$) further support the formation of the instability-driven X-shaped bar/bulge from the thin disk.

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Haopeng Zhang, Yuqin Chen, Gang Zhao, Jingkun Zhao, Xilong Liang, Haining Li, Yaqian Wu, Ali Luo, Rui Wang. 2021-02-11. High-{\alpha}-Metal-Rich stars in the LAMOST-MRS survey and its connection with the galactic bulge. https://doi.org/10.1088/1674-4527%2F21%2F6%2F153

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