Speaker
Description
Vertical stellar kinematics provide a primary probe of the Galactic disk’s mass density and the local dark-matter content, typically under the assumption of dynamical equilibrium. However, a persistent discrepancy exists between densities inferred from stellar kinematics and an independent constraint derived from paleoclimatic records that trace the Solar System’s motion through the Galaxy.
I will show that this apparent tension arises naturally when the effects of spiral-arm shocks are neglected. These shocks act as non-adiabatic perturbations, impulsively heating stellar vertical motions and distorting the local phase-space distribution. Ignoring such time-dependent dynamics leads to systematic biases in equilibrium-based density estimates.
I will present the observational evidence, quantify the discrepancy, and model the impact of spiral-arm perturbations. This framework reconciles kinematic and paleoclimatic measurements, explains the observed vertical heating of stars, and reveals clear signatures in the GAIA phase space—showing that the Galactic disk is not in equilibrium, but a dynamically active system that periodically kicks back at the stars—and at our attempts to weigh it.
