Migration of Gas Giant Planets in Gravitationally Unstable Disks

TL;DR

This study uses 3D radiative hydrodynamics simulations to analyze how gas giant planets migrate within gravitationally unstable disks, revealing complex inward and outward movements influenced by disk modes and instabilities.

Contribution

It provides new insights into the migration behavior of gas giants in gravitationally unstable disks through detailed 3D simulations, highlighting the interaction with disk modes and the resulting migration patterns.

Findings

Planet migration can be rapid and oscillatory, both inward and outward.

Migration often stalls near the inner Lindblad resonance of dominant modes.

Planet eccentricities fluctuate significantly during disk instabilities.

Abstract

Characterization of migration in gravitationally unstable disks is necessary to understand the fate of protoplanets formed by disk instability. As part of a larger study, we are using a 3D radiative hydrodynamics code to investigate how an embedded gas giant planet interacts with a gas disk that undergoes gravitational instabilities (GIs). This Letter presents results from simulations with a Jupiter-mass planet placed in orbit at 25 AU within a 0.14 $M_{\odot}$ disk. The disk spans 5 to 40 AU around a 1 $M_{\odot}$ star and is initially marginally unstable. In one simulation, the planet is inserted prior to the eruption of GIs; in another, it is inserted only after the disk has settled into a quasi-steady GI-active state, where heating by GIs roughly balances radiative cooling. When the planet is present from the beginning, its own wake stimulates growth of a particular global mode with which it strongly interacts, and the planet plunges inward six AU in about 10$^3$ years. In both cases with embedded planets, there are times when the planet's radial motion is slow and varies in direction. At other times, when the planet appears to be interacting with strong spiral modes, migration both inward and outward can be relatively rapid, covering several AUs over hundreds of years. Migration in both cases appears to stall near the inner Lindblad resonance of a dominant low-order mode. Planet orbit eccentricities fluctuate rapidly between about 0.02 to 0.1 throughout the GI-active phases of the simulations.