Concurrent Accretion and Migration of Giant Planets in their Natal Disks with Consistent Accretion Torque. II. Parameter Survey and Condition for Outward Migration

Abstract Migration typically occurs during the formation of planets and is closely linked to the planetary formation process. In classical theories of nonaccreting planetary migration, both type I and type II migration typically result in inward migration, which is hard to align with the architecture of planetary systems. In this work, we conduct systematic, high-resolution 3D/2D numerical hydrodynamic simulations to investigate the migration of an accreting planet. Under different disk conditions, we compared the dynamical evolution of planets with different planet-to-star mass ratios. We find that accretion of planets can significantly diminish the inward migration tendency of planets, or even change the direction of migration. The migration of low-/high-mass planets is classified as type I/II inward migration, respectively, while intermediate-mass planets, which have the strongest accretion, show an outward migration trend. We confirm that the outward migration is mainly attributed to the positive torque from the azimuthal asymmetric structures around the accreting planet, similar to Y.-P. Li et al. The termination of planetary mass growth is thus synonymous with the transition from outward to inward migration. For the cases of high viscosity α = 0.04 and disk aspect ratio h 0 = 0.05, the range of mass ratio for planetary outward migration is 1 × 10 −4 ≲ q ≲ 4 × 10 −3 . For the case of low viscosity with α = 0.001 and/or low disk aspect ratio h 0 = 0.03, the range of mass ratio for outward migration will shift toward the lower end. Our parameter survey reveals that a simple gap-opening parameter determines the condition for outward migration; details of the analytical interpretation are presented by S. Ida et al.