Spatial metallicity variations of mono-temperature stellar populations revealed by early-type stars in LAMOST

Abstract

We investigate the radial metallicity gradients and azimuthal metallicity distributions on the Galactocentric $X$--$Y$ plane using mono-temperature stellar populations selected from LAMOST MRS young stellar sample. The estimated radial metallicity gradient ranges from $-$0.015\,dex/kpc to $-$0.07\,dex/kpc, which decreases as effective temperature decreases (or stellar age increases) at $7500<T_{\mathrm{eff}}<12500$\,K ($\tau <$1.5 Gyr). The azimuthal metallicity excess (metallicity after subtracting radial metallicity gradient, $\Delta$\,[M/H]) distributions exhibit inhomogeneities with dispersions of 0.04\,dex to 0.07\,dex, which decrease as 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 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.

14 pages, 12 figures, Accepted for publication in A&A

References in corpus (15)

• Estimating distances from parallaxes. V: Geometric and photogeometric distances to 1.47 billion stars in Gaia Early Data Release 3
• New constraints on the chemical evolution of the solar neighbourhood and Galactic disc(s). Improved astrophysical parameters for the Geneva-Copenhagen Survey
• Trigonometric Parallaxes Of High-Mass Star Forming Regions: Our View Of The Milky Way
• The evolution of the Galactic metallicity gradient from high-resolution spectroscopy of open clusters
• Mapping metallicity variations across nearby galaxy disks
• Stellar labels for hot stars from low-resolution spectra - I. the HotPayne method and results for 330,000 stars from LAMOST DR6
• The Chemical Evolution Carousel of Spiral Galaxies: Azimuthal Variations of Oxygen Abundance in NGC1365
• Chemical gradients in the Milky Way from the RAVE data. II. Giant stars
• Large Metallicity Variations in the Galactic Interstellar Medium
• Mapping Luminous Hot Stars in the Galaxy
• LAMOST meets Gaia: The Galactic Open Clusters
• Quantifying radial migration in the Milky Way: Inefficient over short timescales but essential to the very outer disc beyond ~15 kpc
• Chemical Cartography with LAMOST and Gaia Reveal Azimuthal and Spiral Structure in the Galactic Disk
• The chemical signature of the Galactic spiral arms revealed by Gaia DR3
• Exploring the stellar rotation of early-type stars in the LAMOST Medium-Resolution Survey. I. Catalog

Cited by in corpus (2)

• Exploring the Stellar Rotation of Early-type Stars in the LAMOST Medium-resolution Survey. III. Evolution
• Revisiting the Radial Metallicity Gradient-Age Relation in the Milky Way's Thin and Thick Disks