Mapping the Galactic Disk with the LAMOST and Gaia Red Clump Sample VII: the Stellar Disk Structure Revealed by the Mono-abundance Populations

TL;DR

This study uses a large sample of red clump stars from LAMOST and Gaia to map the Milky Way's disk structure, revealing distinct mono-abundance populations with different spatial and kinematic properties, including disk flaring.

Contribution

It provides a detailed analysis of the Galactic disk's structure by dividing stars into mono-abundance populations, highlighting their spatial distribution and kinematic differences, which advances understanding of disk formation.

Findings

Identification of two main stellar populations with distinct chemical signatures.

Detection of disk flaring in both high- and low-[α/Fe] populations.

Different radial and rotational profiles for the mono-abundance populations.

Abstract

Using a sample of 96,201 primary red clump (RC) stars selected from the LAMOST and Gaia surveys, we investigate the stellar structure of the Galactic disk. The sample stars show two separated sequences of high-[{\alpha}/Fe] and low-[{\alpha}/Fe] in the [{\alpha}/Fe]-[Fe/H] plane. We divide the sample stars into five mono-abundance populations (MAPs) with different ranges of [{\alpha}/Fe] and [Fe/H], named as the high-[{\alpha}/Fe], high-[{\alpha}/Fe] & high-[Fe/H], low-[Fe/H], solar, high-[Fe/H] MAPs respectively. We present the stellar number density distributions in the R R Z plane, and the scale heights and scale lengths of the individual MAPs by fitting their vertical and radial density profiles. The vertical profiles, the variation trend of scale height with the Galactocentric radius, indicate that there is a clear disk flare in the outer disk both for the low-[{\alpha}/Fe] and the high-[{\alpha}/Fe] MAPs. While the radial surface density profiles show a peak radius of 7 kpc and 8 kpc for the high-[{\alpha}/Fe] and low-[{\alpha}/Fe] MAPs, respectively. We also investigate the correlation between the mean rotation velocity and metallicity of the individual MAPs, and find that the mean rotation velocities are well separated and show different trends between the high-[{\alpha}/Fe] and the low-[{\alpha}/Fe] MAPs. At last, we discuss the character of the high-[{\alpha}/Fe] & high-[Fe/H] MAP and find that it is more similar to the high-[{\alpha}/Fe] MAP either in the radial and vertical density profiles or in the rotation velocity.