Impacts of viscous dissipation on collisional growth and fragmentation of dust aggregates

TL;DR

This study investigates how viscous dissipation influences the collisional outcomes of dust aggregates, revealing that while fragmentation thresholds are unaffected, fragment size distributions are significantly impacted, with implications for planetesimal formation.

Contribution

It provides the first detailed analysis of viscous dissipation effects on dust aggregate collisions, including empirical formulas for fragment size distributions under strong dissipation.

Findings

Fragmentation threshold velocity is unaffected by viscous dissipation in oblique collisions.

Fragment size distribution varies significantly with viscous dissipation strength.

Empirical formulas for fragment size distribution are derived for strong dissipation cases.

Abstract

Understanding the collisional behavior of dust aggregates consisting of submicron-sized grains is essential to unveiling how planetesimals formed in protoplanetary disks. It is known that the collisional behavior of individual dust particles strongly depends on the strength of viscous dissipation force; however, impacts of viscous dissipation on the collisional behavior of dust aggregates have not been studied in detail, especially for the cases of oblique collisions. Here we investigated the impacts of viscous dissipation on the collisional behavior of dust aggregates. We performed numerical simulations of collisions between two equal-mass dust aggregates with various collision velocities and impact parameters. We also changed the strength of viscous dissipation force systematically. We found that the threshold collision velocity for the fragmentation of dust aggregates barely depends on the strength of viscous dissipation force when we consider oblique collisions. In contrast, the size distribution of fragments changes significantly when the viscous dissipation force is considered. We obtained the empirical fitting formulae for the size distribution of fragments for the case of strong dissipation, which would be useful to study the evolution of size and spatial distributions of dust aggregates in protoplanetary disks.