Looking for signatures of minor mergers in the Milky Way thick disc kinematics

Facundo Gomez

Michigan State University

In this talk I will summarize recent results concerning the response of a galactic disc to a minor merger event. As a consequence of the tidal interaction, non-self-gravitating, spiral-like features are induced in the thick disc. Previous studies have shown that this perturbation also leaves an imprint in velocity space (the u-v plane) in small spatial regions, such as the solar neighborhood. This mechanism, known as “ringing”, could explain the presence of high velocity streams observed in the Solar Neighborhood, such as the Arcturus stream. As the disc relaxes after the event, clumps in the u-v plane get closer with time, allowing us to estimate the time of impact. I will show that the space defined by the energy and angular momentum of stars is a better choice than velocity space, as clumps remain visible even in large local volumes. This makes their observational detection much easier since one need not be restricted to a small spatial volume. I will also discuss preliminary results on our attempt to identify signatures of "ringing" in the Milky Way thick disc using a full 6D phase-space sample of G-type dwarfs included in SDSS Data Release 8 (see Lee et al. 2011).