The nature of kinematic structures in the Galactic disk and halo

The Milky Way contains a complex plethora of kinematic structures, that is groups of stars that share a common motion. Although the origin of many kinematic groups are unknown and some widely debated, many of the known kinematic structures can be explained with one or several of the following hypotheses: dissolving star clusters; dynamical resonances between stars and the Galactic bar and/or spiral arms; extragalactic origin via merger events; or phase mixing due to galactic accretion events. Therefore, one of the approaches to try to understand the detailed structure of the Milky Way has been to search for and characterize such kinematic structures.

In this talk I will review main reasons why some stars form kinematic structures, I will show how to characterize some selected kinematic structures in the Milky Way’s disk and halo using large-scale astrometric and spectroscopic surveys, and I will explain how this information can be used to better understand Galaxy formation and evolution.