Constraining the masses of planets in protoplanetary discs from the presence or absence of vortices -- Comparison with ALMA observations

TL;DR

This study explores how the growth timescale of planets in protoplanetary discs influences vortex formation, providing a method to constrain planet masses based on vortex presence or absence in observations.

Contribution

It introduces an approximate relation between planet mass, viscosity, and growth timescale to explain vortex formation, aiding interpretation of observational data.

Findings

Vortices form for planets as small as Neptune mass in low-viscosity discs.

Absence of vortices can exclude certain planet mass and growth timescale combinations.

The relation helps interpret ALMA observations of protoplanetary discs.

Abstract

A massive planet in a protoplanetary disc will open a gap in the disc material. A steep gap edge can be hydrodynamically unstable, which results in the formation of vortices that can act as tracers for the presence of planets in observational results. However, in a viscous disc, the potential formation of these vortices is dependent on the timescale over which the massive planet accretes mass and with a sufficiently long timescale it is possible for no vortices to form. Hence, there is a connection between the presence of vortices and the growth timescale of the planet and it may therefore be possible to exclude a planetary interpretation of observed structure from the absence of vortices. We have investigated the effect of the planet growth timescale on vortex formation for a range of planet masses and viscosities and have found an approximate relation between the planet mass, viscosity and planet growth timescale for which vortices are not formed within the disc. We then interpret these results in the light of recent observations. We have also found that planets do not need to be close to a Jupiter mass to form vortices in the disc if these discs have low viscosity, as these can be caused by planets as small as a few Neptune masses.