Oral Presentation
The messy left-overs of star formation: Morphological, kinematic, and chemical signatures of infall
Presenter: Josh Calcino (Tsinghua University)
Protoplanetary discs are often treated as isolated systems, yet observations increasingly reveal ambient material in their immediate surroundings. These messy leftovers of star formation may continue to feed and perturb discs long after the main collapse phase, but how this material interacts with the disc — and how we should identify it observationally — remains poorly understood. This is complicated by the fact that infall is not a single process: material may arrive through coherent accretion streamers, cloudlet capture, or Bondi–Hoyle–Lyttleton accretion, each with distinct dynamical and chemical signatures.
I will present hydrodynamical simulations showing that streamer-driven infall can excite long-lived spiral structure and produce CO kinematic signatures resembling those often attributed to gravitational instability, including radially converging flows. Applied to AB Aur, this framework provides a striking match to the observed morphology and kinematics without requiring the disc to be gravitationally unstable. In addition, using simulations of Bondi–Hoyle–Lyttleton streamers and a 3D adaptation of a PDR chemical network, we have built a pipeline to make predictions for chemical tracers of infall. Preliminary results suggest that infall events strong enough to leave observable signatures in scattered light and gas kinematics may actually be completely invisible in CO, depending on the UV environment around the recipient star.
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