Collisional Growth and Fragmentation of Dust Aggregates with Low Mass Ratios. I: Critical Collision Velocity for Water Ice

TL;DR

This study uses N-body simulations to explore how icy dust aggregates grow or fragment upon collision, revealing that unequal-mass collisions lower the critical velocity for fragmentation, impacting dust growth in protoplanetary disks.

Contribution

It provides new insights into the critical collision velocities for icy dust aggregates with varying mass ratios, highlighting the role of mass transfer in dust growth processes.

Findings

Mass transfer dominates collisions with mass ratios 2-30.

Critical fragmentation velocity is reduced for unequal-mass collisions.

Higher mass ratios lead to higher impact velocities in protoplanetary disks.

Abstract

We investigated fundamental processes of collisional sticking and fragmentation of dust aggregates by carrying out N-body simulations of submicron-sized icy dust monomers. We examined the condition for collisional growth of two colliding dust aggregates in a wide range of the mass ratio, 1-64. We found that the mass transfer from a larger dust aggregate to a smaller one is a dominant process in collisions with a mass ratio of 2-30 and impact velocity of \approx 30-170 m s^-1. As a result, the critical velocity, v_fra, for fragmentation of the largest body is considerably reduced for such unequal-mass collisions; v_fra of collisions with a mass ratio of 3 is about half of that obtained from equal-mass collisions. The impact velocity is generally higher for collisions between dust aggregates with higher mass ratios because of the difference between the radial drift velocities in the typical condition of protoplanetary disks. Therefore, the reduced v_fra for unequal-mass collisions would delay growth of dust grains in the inner region of protoplanetary disks.