Two mechanisms for dust gap opening in protoplanetary discs

TL;DR

This paper identifies two distinct physical mechanisms by which embedded planets can open dust gaps in protoplanetary discs, highlighting differences in their effects on gas and dust distributions.

Contribution

The study introduces two novel mechanisms for dust gap formation, clarifying how low and high mass planets differently influence dust and gas in protoplanetary discs.

Findings

Low mass planets open dust gaps without disturbing gas.

High mass planets create gas pressure maxima that evacuate dust.

Dust gaps can exist without corresponding gas gaps.

Abstract

We identify two distinct physical mechanisms for dust gap opening by embedded planets in protoplanetary discs based on the symmetry of the drag-induced motion around the planet: I) A mechanism where low mass planets, that do not disturb the gas, open gaps in dust by tidal torques assisted by drag in the inner disc, but resisted by drag in the outer disc; and II) The usual, drag assisted, mechanism where higher mass planets create pressure maxima in the gas disc which the drag torque then acts to evacuate further in the dust. The first mechanism produces gaps in dust but not gas, while the second produces partial or total gas gaps which are deeper in the dust phase. Dust gaps do not necessarily indicate gas gaps.