Flux-Limited Diffusion Approximation Models of Giant Planet Formation by Disk Instability

TL;DR

This study uses advanced 3D radiative hydrodynamics models with flux-limited diffusion to investigate giant planet formation via disk instability, finding that radiative transfer treatment influences temperature but not the formation of self-gravitating clumps.

Contribution

The paper introduces new 3D models with flux-limited diffusion to assess its impact on disk instability and giant planet formation, highlighting the robustness of clump formation across different radiative transfer methods.

Findings

Flux-limited models show higher midplane temperatures.

Self-gravitating clumps form rapidly regardless of radiative transfer method.

Differences in outcomes are likely due to numerical effects, not radiative transfer handling.

Abstract

Both core accretion and disk instability appear to be required as formation mechanisms in order to explain the entire range of giant planets found in extrasolar planetary systems. Disk instability is based on the formation of clumps in a marginally-gravitationally unstable protoplanetary disk. These clumps can only be expected to contract and survive to become protoplanets if they are able to lose thermal energy through a combination of convection and radiative cooling. Here we present several new three dimensional, radiative hydrodynamics models of self-gravitating protoplanetary disks, where radiative transfer is handled in the flux-limited diffusion approximation. We show that while the flux-limited models lead to higher midplane temperatures than in a diffusion approximation model without the flux-limiter, the difference in temperatures does not appear to be sufficiently high to have any significant effect on the formation of self-gravitating clumps. Self-gravitating clumps form rapidly in the models both with and without the flux-limiter. These models suggest that the reason for the different outcomes of numerical models of disk instability by different groups cannot be attributed solely to the handling of radiative transfer, but rather appears to be caused by a range of numerical effects and assumptions. Given the observational imperative to have disk instability form at least some extrasolar planets, these models imply that disk instability remains as a viable giant planet formation mechanism.