Concurrent Accretion and Migration of Giant Planets in their Natal Disks with Consistent Accretion Torque

TL;DR

This study uses high-resolution simulations to show that accreting giant planets can migrate outward due to asymmetric spiral arms, with migration direction depending on disk viscosity, challenging traditional inward migration models.

Contribution

It provides the first self-consistent simulation evidence that accreting giant planets can migrate outward, influenced by accretion and disk viscosity effects.

Findings

Accreting planets tend to migrate outward in viscous disks.

Outward migration is driven by asymmetric spiral arms feeding the Hill sphere.

Transition from outward to inward migration occurs at viscosity parameter α~0.003.

Abstract

Migration commonly occurs during the epoch of planet formation. For emerging gas giant planets, it proceeds concurrently with their growth through the accretion of gas from their natal protoplanetary disks. Similar migration process should also be applied to the stellar-mass black holes embedded in active galactic nucleus disks. In this work, we perform high resolution 3D and 2D numerical hydrodynamical simulations to study the migration dynamics for accreting embedded objects over the disk viscous timescales in a self-consistent manner. We find that an accreting planet embedded in a predominantly viscous disk has a tendency to migrate outward, in contrast to the inward orbital decay of non-accreting planets. 3D and 2D simulations find the consistent outward migration results for the accreting planets. Under this circumstance, the accreting planet's outward migration is mainly due to the asymmetric spiral arms feeding from the global disk into the Hill radius. This is analogous to the unsaturated corotation torque although the imbalance is due to material accretion within the libration timescale rather than diffusion onto the inner disk. In a disk with a relatively small viscosity, the accreting planets clear deep gaps near their orbits. The tendency of inward migration is recovered, albeit with suppressed rates. By performing a parameter survey with a range of disks' viscosity, we find that the transition from outward to inward migration occurs with the effective viscous efficiency factor $\alpha\sim 0.003$ for Jupiter-mass planets.