EPoS Contribution

Mixing is easy: new insights on gas and dust dynamics during disc formation Asmita Bhandare USM, LMU, Munich, DE
Signposts of early planet formation are widespread in sub-structured young discs. Our aim is to constrain the role of gas and dust interaction and resolve potential zones of dust concentration during low-mass star and disc formation stages. We simulate the collapse of dusty molecular cloud cores with the hydrodynamics code PLUTO augmented with radiation transport and self-gravity. The 1, 10 and 100 micron-sized neutral spherical dust grains are treated as Lagrangian particles that are subject to drag from the gas, whose motion is computed on a Eulerian grid. Our study highlights mechanisms for the early transport of well-coupled dust from the inner hot disc regions via the occurrence of two transient gas motions, namely, meridional flow and outflow. The vortical flow fosters dynamical mixing and retention of dust, while the thermal pressure driven outflow replenishes dust in the outer disc. Dust transport, especially, from sub-au scales surrounding the protostar to the outer, relatively cooler parts, offers an efficient pathway for thermal reprocessing during pre-stellar core collapse. We find that young dynamical precursors to planet-forming discs exhibit regions with complex hydrodynamical gas features and high-temperature structures. These can play a crucial role in creating dust pockets that provide building blocks for subsequent growth into protoplanets.

Caption: Top left: 2D view of the first hydrostatic core evolved into a rotationally supported disc at 1221 years after its formation as a result of a 1 M_sun pre-stellar core collapse. The meridional flow exhibited in the plot between 5–10 au forms in the inner regions and travels outwards. This motion results in an outward transport and eventually retains dust in the outer disc. Top right: Selected sample of 1, 10 and 100 micron dust lifted from within the young disc by a thermal pressure driven outflow launched from the vicinity of the protostar. Bottom: Temporal evolution of the dust providing a clear indication of thermal reprocessing within the young disc. The colourmap is split below and above silicate sublimation at 1400 K and indicates the gas temperature at dust location. Tracks are shown for a selected sample of 1 micron dust that end up within the disc. Horizontal dashed black line marks the disc radius. Vertical lines mark the formation time of the nested discs, outflow and merger of the discs from the onset of the first core formation (t=0).
Collaborators: Commerçon B., CRAL/ENS, FR Laibe G., CRAL/ENS, FR Flock M., MPIA, DE Kuiper R., UDE, DE Henning Th., MPIA, DE Mignone A., Univ. Torino, IT Marleau G. D., UDE, DE	Relevant topic(s): Collapse Disks Low-Mass SF
Relevant Big Question: Can dynamical mixing and dust transport via gas flows promote early planet formation within young discs?