Seminar by Josh Calcino, Tsinghua University
Observations of protoplanetary discs across a range of evolutionary stages increasingly reveal ambient material in their immediate surroundings, suggesting that discs may continue to interact with their natal environment after the main phase of star formation. However, how this material couples to the disc, and what observable signatures it produces, is not fully understood.
In this talk, I will present hydrodynamical simulations of infalling streamers onto protoplanetary discs. These simulations show that streamer-driven infall can excite abundant spiral structure, including spirals that appear stationary in observations and persist long after the infall event. I will also show that infall can produce CO kinematic signatures resembling those commonly attributed to gravitational instability, including spiral-like velocity residuals and radially converging flows. Applied to AB Aur, this framework provides a striking match to the system’s complex morphology and kinematics without requiring the disc to be gravitationally unstable. I will then discuss ongoing work on the chemistry of infalling material. Using FARGO3D simulations of Bondi–Hoyle–Lyttleton streamers from Huhn et al. and a 3D adaptation of a PDR chemical network, I have built a pipeline to make predictions for chemical abundances of Bondi-Hoyle-Lyttleton infall. Complementary 1D slab models suggest that CO can be fully dissociated at densities typical of BHL streamers, depending sensitively on the stellar UV field and accretion luminosity. My results suggest that infall events strong enough to leave observable signatures in scattered light and gas kinematics may actually be completely invisible in CO.
Host: Jane Huang