Long-lasting dust rings in gas-rich disks: sculpting by single and multiple planets

TL;DR

This paper investigates how dust rings in protoplanetary disks can form and persist longer than gas rings due to pressure maxima created by planets, with simulations showing dust trapping and decoupling effects.

Contribution

It introduces a mechanism involving planetary gaps and pressure maxima that explains long-lasting dust rings, supported by 2D hydrodynamical simulations.

Findings

Dust rings form between planets or at gap edges due to pressure maxima.

Large dust particles decouple from gas and remain in rings longer.

Trapping and decoupling are most effective for millimeter and centimeter grains at ~10 au.

Abstract

We propose a mechanism by which dust rings in protoplanetary disks can form and be long-lasting compared to gas rings. This involves the existence of a pressure maximum which traps dust either in between two gap-opening planets or at the outermost gap edge of a single or multiple planet system, combined with the decoupling of large dust particles from the gas. We perform 2D gas hydrodynamical simulations of disks with one and two giant planets which may open deep or partial gaps. A gas ring forms in between two planets such that the surface mass density is higher than on either side of it. This ring is a region of pressure maximum where we expect large grains, which are marginally coupled to the gas and would otherwise be subject to radial drift, to collect. Such a pressure maximum also occurs at the outermost gap edge in a disk with one or more planets. We infer the dust evolution in these regions as the gas disk evolves, to understand the longer term behavior of the resulting dust rings. Over time the gas surface density in the ring(s) decreases, which may cause the larger trapped particles to decouple. Consequently, these particles are expected to stay in ring structure(s) longer than the gas. For a Minimum Mass Solar Nebula model, we expect that millimeter and centimeter-sized grains in the outer O(10) au would most likely undergo this trapping and decoupling process.