Is the Milky Way ringing? The hunt for high velocity streams
  We perform numerical simulations of a stellar galactic disk with initial
conditions chosen to represent an unrelaxed population which might have been
left following a merger. Stars are unevenly distributed in radial action angle,
though the disk is axisymmetric. The velocity distribution in the simulated
Solar neighborhood exhibits waves traveling in the direction of positive v,
where u,v are the radial and tangential velocity components. As the system
relaxes and structure wraps in phase space, the features seen in the uv-plane
move closer together. We show that these results can be obtained also by a
semi-analytical method. We propose that this model could provide an explanation
for the high velocity streams seen in the Solar neighborhood at approximate v
in km/s, of -60 (HR 1614), -80 (Arifyanto and Fuchs 2006), -100 (Arcturus), and
-160 (Klement et al. 2008). In addition, we predict four new features at v ~
-140, -120, 40 and 60 km/s. By matching the number and positions of the
observed streams, we estimate that the Milky Way disk was strongly perturbed
~1.9 Gyr ago. This event could have been associated with Galactic bar
formation.
