2024ApJS..272....8S

A detailed measurement is made of the metallicity distributions, kinematics, and dynamics of the thin and thick disks across a large disk volume (5.0 ≤ R ≤ 15.0 kpc and ∣Z∣ ≤ 3.0 kpc) by using the LAMOST-APOGEE red clump stars. The metallicity distribution results show that the radial metallicity gradient Δ[Fe/H]/ΔR of the thin disk weakens with ∣Z∣ from -0.06 dex kpc^–1 at around ∣Z∣ < 0.25 kpc to -0.02 dex kpc^–1 at around ∣Z∣ > 2.75 kpc, while the thick disk displays a global weak positive Δ[Fe/H]/ΔR that is generally weaker than 0.01 dex kpc^–1. The vertical metallicity gradient Δ[Fe/H]/Δ∣Z∣ steadily weakened from -0.36 dex kpc^–1 at R ∼ 5.5 kpc to -0.05 dex kpc^–1 at around R > 11.5 kpc for the thin disk, while the thick disk presents an almost constant value (nearly -0.06∼-0.08 dex kpc^–1) for all the R bins. These results indicate the contribution of the radial migration to the disk evolution, and the obvious north-south asymmetry in [Fe/H] may be linked to disk warp and/or disk perturbation events. The oscillations in the corrected Δ[Fe/H]/Δ∣Z∣ with R likely arise from the resonances with the Galactic bar. Our detailed measurements of ΔV_ϕ/Δ[Fe/H] indicate an inside-out and upside-down star formation scenario for the thick disk. The results of eccentricity distributions and [α/Fe]-velocity dispersion relations are likely to suggest that thick-disk stars require an obvious contribution from other heating mechanisms, such as mergers and accretion, or are born in the chaotic mergers of gas-rich systems and/or the turbulent interstellar medium.