Dust dynamics in 2D gravito-turbulent disks

TL;DR

This study investigates how gravito-turbulence in protoplanetary disks influences dust particle dynamics, showing that it hinders large particle growth but promotes formation of planetesimals from intermediate-sized particles through gravitational collapse.

Contribution

It provides the first detailed analysis of dust behavior in gravito-turbulent disks using 2D hybrid simulations, highlighting differences from MRI-driven turbulence.

Findings

Large particles experience stronger stirring and higher relative speeds in gravito-turbulent disks.

Agglomeration of large particles into planetesimals is disfavored due to high collision speeds.

Intermediate-sized particles can form dense filaments leading to gravitational collapse and planetesimal formation.

Abstract

The dynamics of solid bodies in protoplanetary disks are subject to the properties of any underlying gas turbulence. Turbulence driven by disk self-gravity shows features distinct from those driven by the magnetorotational instability (MRI). We study the dynamics of solids in gravito-turbulent disks with two-dimensional (in the disk plane), hybrid (particle and gas) simulations. Gravito-turbulent disks can exhibit stronger gravitational stirring than MRI-active disks, resulting in greater radial diffusion and larger eccentricities and relative speeds for large particles (those with dimensionless stopping times $t_{stop} \Omega > 1$, where $\Omega$ is the orbital frequency). The agglomeration of large particles into planetesimals by pairwise collisions is therefore disfavored in gravito-turbulent disks. However, the relative speeds of intermediate-size particles $t_{stop} \Omega \sim 1$ are significantly reduced as such particles are collected by gas drag and gas gravity into coherent filament-like structures with densities high enough to trigger gravitational collapse. First-generation planetesimals may form via gravitational instability of dust in marginally gravitationally unstable gas disks.