Puffed up Edges of Planet-opened Gaps in Protoplanetary Disks. I. hydrodynamic simulations

TL;DR

This study uses 3D hydrodynamic simulations to show that massive planets can cause dust grains to puff up at gap edges, affecting the interpretation of observed dust rings in protoplanetary disks.

Contribution

It demonstrates the vertical stirring of sub-mm-sized dust grains by planet-induced flows, highlighting the need for 3D modeling in disk-planet interaction studies.

Findings

Dust scale-height can reach ~70% of gas scale-height at gap edges.

Planet-induced flows cause significant dust puff-up, affecting dust ring sharpness.

Large grains (>mm) are necessary for consistent gas-gap interpretation.

Abstract

Dust gaps and rings appear ubiquitous in bright protoplanetary disks. Disk-planet interaction with dust-trapping at the edges of planet-induced gaps is one plausible explanation. However, the sharpness of some observed dust rings indicate that sub-mm-sized dust grains have settled to a thin layer in some systems. We test whether or not such dust around gas gaps opened by planets can remain settled by performing three-dimensional, dust-plus-gas simulations of protoplanetary disks with an embedded planet. We find planets massive enough to open gas gaps stir small, sub-mm-sized dust grains to high disk elevations at the gap edges, where the dust scale-height can reach ~70% of the gas scale-height. We attribute this dust 'puff-up' to the planet-induced meridional gas flows previously identified by Fung & Chiang and others. We thus emphasize the importance of explicit 3D simulations to obtain the vertical distribution of sub-mm-sized grains around gas gaps opened by massive planets. We caution that the gas-gap-opening planet interpretation of well-defined dust rings is only self-consistent with large grains exceeding mm in size.