The disturbed outer Milky Way disc

ABSTRACT The outer parts of the Milky Way’s disc are significantly out equilibrium. Using only distances and proper motions stars from Gaia’s Early Data Release 3, in range |b| < 10°, 130° ? 230°, we show that for between around 10 $14\, \mathrm{kpc}$ Galactic centre, vertical velocity is strongly dependent on angular momentum, azimuth, position above or below plane. We further how this behaviour translates into a bimodality distribution Way disc. use an N-body model impulse-like interaction with perturber similar to Sagittarius dwarf demonstrate mechanism can generate disturbance. It has already been shown produce phase spiral seen Solar neighbourhood. argue details substructure galaxy will be highly sensitive timing perturbation gravitational potential Galaxy, therefore may key disentangling history structure Way.