Description
It has been demonstrated in many simulations that secular evolution driven by non-axisymmetric structures is crucial to the evolution of disc galaxies. The Galactic bar, as a dominant non-axisymmetric structure in many disc galaxies, has been studied intensively in simulations. With Gaia DR3, we can now begin to study the imprints that the Galactic bar has left on the Milky Way disc to test previous results obtained from simulations. In this talk, I will discuss the time-resolved picture of both the inner and outer Milky Way disc and their correlation with bar-driven secular evolution
In the inner disc, we map the chrono-kinematic evolution using Mira variables. We see evidence that bar-like kinematics exists ubiquitously in all stellar populations younger than 11 Gyr, significantly older than the estimated age of the Galactic bar, and that younger stars exhibit stronger bar signatures. This is a consequence of the kinematic fragmentation, where all disc populations can be trapped into bar-like orbits in a barred potential, and kinematically colder populations respond more effectively to the galactic bar.
In the outer disc, we present evidence of radial migration driven by corotation resonance dragging from a slowing bar, a star dragged from the inner to the outer disc by the expansion of the corotation radius. We show that the expected age–metallicity pattern and its spatial dependence from this mechanism closely match observations. Furthermore, we constrain the pattern speed history of the Galactic bar, assuming this mechanism dominates the radial migration processes in the Milky Way’s disc.
