Event

The origin of the stars with coherent velocities discovered in the solar neighborhood remains uncertain, but their dynamics and evolution are key to understanding the dynamics of the Galactic stellar disk and ultimately the history of the Milky Way. The Gaia satellite is currently mapping the phase-space of a few million stars in the solar neighborhood. About 350,000 stars within 200 pc of the Sun are identified in streams, bundles of stars that move together in the same direction with a velocity that is distinct from neighboring stars. Twenty percent of these stars are part of the Hercules stream. This study presents GALAKOS a high-resolution N-body simulation of the Milky Way disk that accounts for time-varying potential and performs the action and phase-space analysis to reveal the origin of this stream.  We show that Hercules consists of stars trapped at co-rotation with a long stellar bar. As the bar grows in length the torque exerting on the stars induces them to librate around one lagrangian point which is located approximately 1 kpc away from the Sun. While our findings indicate that the Hercules Stream does not consist of stars scattered from the inner part of the Galaxy or at the outer Lindblad resonance as previously thought, I will discuss caveats related to our understanding of moving groups in this scenario.