Title：Modelling the secular evolution of the Milky Way’s disc

Speaker：Hanyuan Zhang

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 recent findings on mapping the Milky Way's secular evolution using main-sequence turn-off stars from LAMOST. I will demonstrate how bar-driven radial migration can reproduce observed bimodal age-metallicity sequences and the α-bimodality. Additionally, I will introduce 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.

Bio:

I am a PhD student at the University of Cambridge working with Prof. Vasily Belokurov. Before that, I was also a master's student at the University of Cambridge and an undergraduate student at Imperial College London. My research interests are in galaxy evolution, in particular, the dynamical evolution of the Milky Way. So far, my PhD focuses on measuring the dynamical structure and evolution of the Galactic bar and disc and using them as a benchmark to understand the secular evolution of galaxies.

Time: 14:00-15:00, 25/December, Thursday 

Venue: Room 502 (Small seminar room), Department of Astronomy