Issue |
A&A
Volume 674, June 2023
|
|
---|---|---|
Article Number | A129 | |
Number of page(s) | 13 | |
Section | Galactic structure, stellar clusters and populations | |
DOI | https://doi.org/10.1051/0004-6361/202245761 | |
Published online | 13 June 2023 |
Spatial metallicity variations of mono-temperature stellar populations revealed by early-type stars in LAMOST
1
Tianjin Astrophysics Center, Tianjin Normal University, Tianjin 300387, PR China
e-mail: wchun@tjnu.edu.cn
2
Department of Astronomy, Beijing Normal University, Beijing 100875, PR China
e-mail: yuanhb@bnu.edu.cn
3
National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, PR China
4
Research School of Astronomy and Astrophysics, Australian National University, Cotter Rd., Weston, ACT 2611, Australia
5
School of Computing, Australian National University, Acton, ACT 2601, Australia
6
South-Western Institute For Astronomy Research, Yunnan University, Kunming 650500, PR China
Received:
22
December
2022
Accepted:
4
April
2023
We investigate the radial metallicity gradients and azimuthal metallicity distributions on the Galactocentric X–Y plane using mono-temperature stellar populations selected from the LAMOST-MRS young stellar sample. The estimated radial metallicity gradient ranges from −0.015 dex/kpc to −0.07 dex/kpc, which decreases as the effective temperature decreases (or when the stellar age increases) at 7500 < Teff < 12 500 K (τ < 1.5 Gyr). The azimuthal metallicity excess (the metallicity after subtracting the radial metallicity gradient, Δ [M/H]) distributions exhibit inhomogeneities with dispersions of 0.04 dex to 0.07 dex, which decrease as the effective temperature decreases. We also identify five potential metal-poor substructures with large metallicity excess dispersions. The metallicity excess distributions of these five metal-poor substructures suggest that they contain a larger fraction of metal-poor stars compared to other control samples. These metal-poor substructures may be associated with high-velocity clouds that infall into the Galactic disk from the Galactic halo, which are not quickly well mixed with the pre-existing interstellar medium (ISM) of the Galactic disk. As a result, these high-velocity clouds produce some metal-poor stars and the observed metal-poor substructures. The variations of metallicity inhomogeneities with different stellar populations indicate that high-velocity clouds are not well mixed with the pre-existing Galactic disk ISM within 0.3 Gyr.
Key words: Galaxy: abundances / Galaxy: disk / Galaxy: evolution
© The Authors 2023
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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