Lunch talk on Sep. 22, 2025

Studying the Milky Way with the GASTRO Simulations

Speaker: João A. S. Amarante (SJTU)

Venue: SWIFAR Building 2111

Time: 12:45 PM, Monday, Sep. 22, 2025

Abstract: 

It is known that a major merger happened during the Milky Way's (MW) first Gyrs and, likely, perturbed its disc-shape structure. To fully understand the effects of such an event, we developed the Gaia-EncelAdus-Sausage Timing, chemistRy and Orbit (GASTRO) library: a suite of SPH + N-body models tailored to explore formation scenarios of Milky Way-like galaxies that went through similar merger events. In this talk, I present a subset of GASTRO models and show how high-density clumps and a single merger modulate the star formation rate of the disc. This modulation leads to the formation of the alpha-rich and alpha-poor populations, similarly to what is observed in the Milky Way. Furthermore, I show that only the models with an early clumpy phase can produce a significant fraction of old, age > 11 Gyr, alpha-poor stars with disc orbits, similar to what has been recently observed in the MW. We propose that this can be the observational constraint linking clumpy discy galaxies observed at redshift z~2 as the likely progenitors of our Galaxy. Finally, I explore the chemodynamical properties of the accreted stars and the implications for the known substructures in the stellar halo of our Galaxy.