Kinematic and Dynamical Properties of Solar-neighborhood White Dwarfs from SDSS Data Release 19 and Gaia Data Release 3

Abstract We present a comprehensive kinematic and dynamical analysis of 5837 white dwarfs with hydrogen-rich atmospheres, SDSS DR19 spectroscopy, and Gaia Data Release 3 astrometry. Using complementary spatial distributions, kinematic properties, and orbital parameters, we show that the sample is overwhelmingly dominated by the thin disk, with only minor contributions from the thick disk and the halo. Velocity dispersions and orbital eccentricities increase systematically from the thin disk to the halo, reflecting progressively hotter Galactic populations. Total stellar ages available for 4829 white dwarfs reveal a clear age–velocity dispersion relation with power-law indices of 0.06–0.17, confirming that white dwarfs preserve the secular dynamical heating history of the Galactic disk. We derive a thin-disk scale height of 123–229 pc and radial scale length of 3.2–3.5 kpc, while the thick disk has a scale height of 865 pc and contributes approximately 6%–7% of the local stellar density. Reconstructed birth radii indicate that changes in the guiding radii represent an important component of the present-day radial redistribution of nearby white dwarfs, although the relative contributions of radial migration and orbital blurring cannot be uniquely separated from these displacement measures. These results establish white dwarfs as powerful tracers of the kinematic, dynamical, and structural evolution of the Milky Way.