2025ApJ...979..103S

Using nearly 230,000 red clump stars selected from LAMOST and Gaia, we conduct a comprehensive analysis of the stellar age-velocity dispersion relations (AVRs) for various disk populations, within 5.0 ≤ R ≤ 15.0 kpc and ∣Z∣ ≤ 3.0 kpc. The AVRs of the whole red clump sample stars are accurately described as σ_v = σ_v,0 (τ + 0.1)${}^{{\beta }_{v}}$, with β_R, β_ϕ, and β_Z displaying a global exponential decreasing trend with R, which may point to the difference in spatial distributions of various disk heating mechanisms. The measurements of β-R for various disks suggest that the thin disk exhibits a radial dependence, with a global exponential decreasing trend in β_R-R and β_Z-R, while β_ϕ remains a nearly constant value (around 0.20 ∼ 0.25) within 8.5 ≤ R ≤ 11.5 kpc. The thick disk displays a global increasing trend in β_R-R, β_ϕ-R, and β_Z-R. These results indicate that the thin disk stars are likely heated by long-term heating from giant molecular clouds and spiral arms, while thick disk stars are likely heated by some violent heating process from merger and accretion, and/or formed by the inside-out and upside-down star formation scenarios, and/or born in the chaotic mergers of gas-rich systems and/or turbulent interstellar medium. Our results also suggest that the disk perturbation by a recent minor merger from Sagittarius may have occurred within 3.0 Gyr.