Friday

The heating of stellar orbits arising from close encounters with nearby giant molecular clouds, globular clusters, and satellite galaxies is encoded in the velocity dispersions and ages of stars. We present new equilibrium dynamical models based on action-based distribution functions that capture the imprint of inside-out growth, radial migration, and vertical heating on the phase-space structure, [Fe/H], [a/Fe], and age of stars in disk galaxies.

We apply the new models to red clumps in the LAMOST spectroscopic survey of the Milky Way, which together with unprecedented photometric and astrometric data collected by Gaia allows the derivation of reliable distances, three-dimensional velocities, and ages of stars far beyond our Sun. The sample contains predominantly young and metal-rich stars and therefore probes the phase-space kinematics of the outer low-alpha disk. By making careful consideration of the complex selection function of LAMOST, we are able to reveal the detailed vertical heating history of the low-alpha disk of the Milky Way.