Planet Migration in Self-Gravitating Discs: Survival of Planets

TL;DR

This study uses 3D simulations to show that planets can survive inward migration in self-gravitating discs due to thermodynamic effects, especially in the inner stable regions, challenging previous simplified models.

Contribution

It demonstrates that thermodynamics significantly influence planet migration, allowing planets to slow down without gap opening in self-gravitating discs, which was not shown in earlier studies.

Findings

Planets initially migrate inward rapidly.

Planets can slow down in stable inner regions.

Thermodynamics crucially affect migration behavior.

Abstract

We carry out three-dimensional SPH simulations to study whether planets can survive in self-gravitating protoplanetary discs. The discs modelled here use a cooling prescription that mimics a real disc which is only gravitationally unstable in the outer regions. We do this by modelling the cooling using a simplified method such that the cooling time in the outer parts of the disc is shorter than in the inner regions, as expected in real discs. We find that both giant (> M_Sat) and low mass (< M_Nep) planets initially migrate inwards very rapidly, but are able to slow down in the inner gravitationally stable regions of the disc without needing to open up a gap. This is in contrast to previous studies where the cooling was modelled in a more simplified manner where regardless of mass, the planets were unable to slow down their inward migration. This shows the important effect the thermodynamics has on planet migration. In a broader context, these results show that planets that form in the early stages of the discs' evolution, when they are still quite massive and self-gravitating, can survive.