Is the ring inside or outside the planet?: The effect of planet migration on dust rings

TL;DR

This study investigates how planet migration affects dust ring formation in protoplanetary discs, proposing observable signatures to determine if a planet is migrating based on dust ring shifts.

Contribution

We demonstrate through hydrodynamical simulations that dust ring locations relative to a migrating planet depend on particle size, providing a potential observational test for planet migration.

Findings

Small dust particles form rings interior to the planet.

Large dust particles form rings exterior to the planet.

A migrating planet causes an outward shift of dust rings at longer wavelengths.

Abstract

Planet migration in protoplanetary discs plays an important role in the longer term evolution of planetary systems, yet we currently have no direct observational test to determine if a planet is migrating in its gaseous disc. We explore the formation and evolution of dust rings - now commonly observed in protoplanetary discs by ALMA - in the presence of relatively low mass (12-60 Earth masses) migrating planets. Through two dimensional hydrodynamical simulations using gas and dust we find that the importance of perturbations in the pressure profile interior and exterior to the planet varies for different particle sizes. For small sizes a dust enhancement occurs interior to the planet, whereas it is exterior to it for large particles. The transition between these two behaviours happens when the dust drift velocity is comparable to the planet migration velocity. We predict that an observational signature of a migrating planet consists of a significant outwards shift of an observed midplane dust ring as the wavelength is increased.