Unveiling the 2D Disk Snowline with Hydrodynamical Simulations

In protoplanetary disks, the water snowline marks the location where inward-drifting ice-rich pebbles sublimate to release dry silicate grains and water vapor. These processes can lead to a dust pile-up (i) inside the snowline when the released silicate grains drift at much lower speeds, causing a “traffic jam” or (ii) outside the snowline when vapor recondenses onto pebbles to enhance the solid mass. For its capability of enhancing the dust-to-gas ratio, the water snowline has been proposed as a likely site for the formation of the first generation of planetesimals, e.g., through streaming instability. Although considerable research has explored conditions favoring dust pile-up, these studies usually employ 1D, vertically-averaged and isothermal assumptions. However, recent analyses of molecular line mission by ALMA’s MAPS collaboration has revealed complex disk thermal structures. We aim to understand how realistic temperature structure in disks influences the snowline dynamics and dust pile-up outcome. We conduct 2D multifluid dust hydrodynamics (Huang & Bai 2022) in the disk’s R-Z plane utilizing the Athena++ framework with an advanced phase change module (Wang et al. 2023). A multi-fluid approach is used to follow chemically heterogeneous pebbles and vapor is followed by a tracer fluid. We adopt a 1+1D radiation transfer method to determine the temperature structure, accounting for irradiated heating, viscous heating and latent heat exchange during ice sublimation. We identify a water recycling pattern across snowline: ice sublimates at the midplane and vapor diffuses to higher altitudes, where it recondenses due to the lower ambient temperatures. This cycle tends to enhance the dust pile-up by trapping upward-diffusing vapor. Our preliminary results also indicate a broad, 2D ice sublimating zone with a temperature plateau due to the latent heat effects. This may have observational implications in continuum/line emission of FU Ori-type disks (E.g., V883 Ori), where snowlines could extend to several tens of AUs.