http://arxiv.org/abs/2305.07426
Phase-space data, chemistry, and ages together reveal a complex structure in the outer low-${\alpha}$ disc of the Milky Way. The age-vertical velocity dispersion profiles beyond the Solar Neighbourhood show a significant jump at 6 Gyr for stars beyond the Galactic plane. Stars older than 6 Gyr are significantly hotter than younger stars. The chemistry and age histograms reveal a bump at [Fe/H] = -0.5, [${\alpha}$/Fe] = 0.1, and an age of 7.2 Gyr in the outer disc. Finally, viewing the stars beyond 13.5 kpc in the age-metallicity plane reveals a faint streak just below this bump, towards lower metallicities at the same age. Given the uncertainty in age, we believe these features are linked and suggest a pericentric passage of a massive satellite 6 Gyr ago that heated pre-existing stars, led to a starburst in existing gas. New stars also formed from the metal-poorer infalling gas. The impulse approximation was used to characterise the interaction with a satellite, finding a mass of ~1e11 M$_{\odot}$, and a pericentric position between 12 and 16 kpc. The evidence points to an interaction with the Sagittarius dwarf galaxy, likely its first pericentric passage.
P. Das, Y. Huang, I. Ciuca, et. al.
Mon, 15 May 23
51/53
Comments: 10 pages, 6 figures, submitted to MNRAS