Collisional Growth of Icy Dust Aggregates in Disk Formation Stage: Difficulties for Planetesimal Formation via Direct Collisional Growth outside the Snowline

TL;DR

This study examines the early stages of protoplanetary disk formation and finds that icy dust aggregates are unlikely to form planetesimals via direct collisions outside the snowline due to radial drift and temperature constraints.

Contribution

It demonstrates that icy dust growth into planetesimals during the disk formation stage is hindered by radial drift and thermal effects, highlighting challenges in early planetesimal formation.

Findings

Icy dust aggregates deplete before forming planetesimals in early disks.

Radial drift restricts dust growth outside the snowline.

Elevated temperatures limit the growth region to inside the snowline.

Abstract

Highly porous dust aggregates can break through the radial drift barrier, but previous studies assumed disks in their later stage, where the disks have a very small mass and low temperature. In contrast, dust coagulation should begin in the very early stage such as the disk formation stage because the growth timescale of dust is shorter than the disk formation timescale if there is no process to suppress the collisional growth of dust. We investigate the possibility of planetesimal formation via direct collisional growth in the very early stage of a protoplanetary disk. We show that, in the very early stage of protoplanetary disks, icy dust aggregates suffer radial drift and deplete without forming planetesimal-sized objects. This is because as the disk temperature easily increases by the viscous heating in the disk formation stage, the area where the dust can break through the radial drift barrier is restricted only to the inside the snowline. This suggests that in the disk formation stage, icy planetesimal formation via direct collisional growth of dust is difficult.