Lunch talk on Dec. 30, 2025

Modelling the secular evolution of the Milky Way’s disc

Speaker: Hanyuan Zhang (SHAO)

Venue: SWIFAR Building 2111

Time: 12:45 PM, Tuesday, Dec. 30, 2025

Abstract: 

Stellar orbits in galactic discs are not static but evolve through gravitational interactions with non-axisymmetric perturbations, such as bars, spirals, and giant molecular clouds. This process, known as secular evolution, efficiently redistributes stars across the disc, thereby mixing chemical signatures from their birthplaces and altering the galaxy's chemodynamical properties. Observationally, the age-metallicity distribution of the Galactic disc offers valuable insights into the Milky Way's secular evolution history. In this talk, I will present our new chemo-chrono-dynamical model of the Galactic disc, which reconstructs its inside-out growth, metallicity evolution, and secular evolution history. Our work reveals a clear transition in radial migration strength, occurring around the epoch of the high- to low-α disc transition. Finally, by comparing these findings with Nexus simulations, I will discuss the implications of the inferred secular evolution history for the Milky Way.