Hiding Signatures of Gravitational Instability in Protoplanetary Discs with Planets

TL;DR

This study uses 3D simulations to demonstrate that migrating giant planets can hide gravitational instability-induced spiral structures in protoplanetary discs, affecting their observational signatures.

Contribution

It shows that giant planets can suppress observable spiral features in self-gravitating discs, providing a new explanation for the absence of such structures in some observations.

Findings

Giant planets suppress spiral structures in self-gravitating discs.

Disc observations without spiral arms can be explained by planetary suppression rather than low disc mass.

Gas kinematics can reveal the presence of planets even when spiral features are hidden.

Abstract

We carry out three dimensional SPH simulations to show that a migrating giant planet strongly suppresses the spiral structure in self-gravitating discs. We present mock ALMA continuum observations which show that in the absence of a planet, spiral arms due to gravitational instability are easily observed. Whereas in the presence of a giant planet, the spiral structures are suppressed by the migrating planet resulting in a largely axisymmetric disc with a ring and gap structure. Our modelling of the gas kinematics shows that the planet's presence could be inferred, for example, using optically thin 13C16O. Our results show that it is not necessary to limit the gas mass of discs by assuming high dust-to-gas mass ratios in order to explain a lack of spiral features that would otherwise be expected in high mass discs.