COLLISIONAL GROWTH CONDITIONS FOR DUST AGGREGATES

TLDR

Collisions between dust aggregates are central to planetesimal formation because they occur naturally in protoplanetary disks. The study investigates whether icy dust aggregates can grow through high‑velocity collisions by running over 4,000 three‑dimensional numerical simulations of BPCA and BCCA clusters with varying impact parameters. Using BPCA clusters with fractal dimension 3 and a compact structure, the simulations determine growth and disruption criteria for compressed aggregates during collisions in protoplanetary disks. Simulations indicate that ice dust aggregates can grow in collisions up to 50 m s⁻¹, with ejecta mass decreasing as aggregate size increases, demonstrating that high‑velocity collisions can still lead to growth and survival in protoplanetary disks.

Abstract

Collisions between dust aggregates are the key to understand the formation of planetesimals because the collision inevitably takes place in protoplanetary disks. To clarify whether or not dust aggregates can grow through their mutual collisions at relatively high velocities, we carry out more than 4000 runs of three-dimensional numerical simulations of collisions between icy equal-mass clusters formed under ballistic particle–cluster aggregation (BPCA) as well as those of ballistic cluster–cluster aggregation, including offset collisions with various values of the impact parameter. Since our BPCA clusters have a fractal dimension of 3 and a relatively compact structure, their results enable us to determine the criteria for growth and disruption of compressed aggregates at their collisions in protoplanetary disks. The results show that ice dust aggregates are able to grow at collisions with velocities up to 50 m s−1, in spite of their initial structures and impact parameters. We also find that the mass of ejecta relative to the total mass of colliding aggregates decreases with increasing the size of the aggregates. These results demonstrate the feasibility of growth and survival for dust aggregates through their mutual collisions with relatively high velocities in protoplanetary disks.