Effects of Thermodynamics on the Concurrent Accretion and Migration of Gas Giants in Protoplanetary Disks

TL;DR

This study uses hydrodynamical simulations to investigate how thermodynamics, especially radiative cooling, influence the simultaneous accretion and migration of gas giants in protoplanetary disks, revealing a critical cooling timescale for migration direction.

Contribution

It introduces a self-consistent model of thermodynamics with a $eta$-cooling prescription to analyze its impact on planet migration and accretion, highlighting the role of cooling timescales.

Findings

Cooling timescales affect accretion rates and migration direction.

Efficient cooling promotes outward migration via asymmetric CPD structures.

Longer cooling times suppress positive torque, leading to inward migration.

Abstract

Accretion and migration usually proceeds concurrently for giant planet formation in the natal protoplanetary disks. Recent works indicate that the concurrent accretion onto a giant planet imposes significant impact on the planetary migration dynamics in the isothermal regime. In this work, we carry out a series of 2D global hydrodynamical simulations with Athena++ to explore the effect of thermodynamics on the concurrent accretion and migration process of the planets in a self-consistent manner. The thermodynamics effect is modeled with a thermal relaxation timescale using a $\beta$-cooling prescription. Our results indicate that radiative cooling has a substantial effect on the accretion and migration processes of the planet. As cooling timescales increase, we observe a slight decrease in the planetary accretion rate, and a transition from the outward migrating into inward migration. This transition occurs approximately when the cooling timescale is comparable to the local dynamical timescale ($\beta\sim1$), which is closely linked to the asymmetric structures from the circumplanetary disk (CPD) region. The asymmetric structures in the CPD region which appear with an efficient cooling provide a strong positive torque driving the planet migrate outward. However, such a positive torque is strongly suppressed, when the CPD structures tend to disappear with a relatively long cooling timescale ($\beta\gtrsim10$). Our findings may also be relevant to the dynamical evolution of accreting stellar-mass objects embedded in disks around active galactic nuclei.