Dust and gas density evolution at a radial pressure bump in protoplanetary disks

TL;DR

This study examines how dust and gas densities evolve at a radial pressure bump in protoplanetary disks, revealing that dust back-reaction deforms the bump and inhibits large-scale planetesimal formation.

Contribution

It demonstrates the impact of dust back-reaction on pressure bump deformation and the suppression of streaming instability-driven large clump formation.

Findings

Pressure bump is deformed when dust-to-gas ratio reaches ~1.

Grain clumps formed by streaming instability are smaller (~1-100 km).

Dust back-reaction inhibits gravitational instability and large planetesimal formation.

Abstract

We investigate the simultaneous evolution of dust and gas density profiles at a radial pressure bump located in a protoplanetary disk. If dust particles are treated as test particles, a radial pressure bump traps dust particles that drift radially inward. As the dust particles become more concentrated at the gas pressure bump, however, the drag force from dust to gas (back-reaction), which is ignored in a test-particle approach, deforms the pressure bump. We find that the pressure bump is completely deformed by the back-reaction when the dust-to-gas mass ratio reaches $\sim 1$ for a slower bump restoration. The direct gravitational instability of dust particles is inhibited by the bump destruction. In the dust-enriched region, the radial pressure support becomes $\sim 10-100$ times lower than the global value set initially. Although the pressure bump is a favorable place for streaming instability (SI), the flattened pressure gradient inhibits SI from forming large particle clumps corresponding to $100-1000$ km sized bodies, which has been previously proposed. If SI occurs there, the dust clumps formed would be $10-100$ times smaller, that is, of about $1 - 100$ km.