On the diversity in mass and orbital radius of giant planets formed via disk instability

TL;DR

This study models the formation and distribution of giant planets via disk instability, revealing that their mass and orbital radius are highly sensitive to model assumptions, with massive distant giants being rare.

Contribution

Introduces a semi-analytical population synthesis model considering various parameters, highlighting the impact of gap opening criteria on planet survival and distribution.

Findings

Surviving clumps are less massive and closer to the star when realistic gap opening is considered.

Planet mass ranges from 0.01 to 16 Jupiter masses, with a preference for 10-30 AU.

Massive giants at very large distances are rare, aligning with direct imaging surveys.

Abstract

We present a semi-analytical population synthesis model of protoplanetary clumps formed by disk instability at radial distances of 80 - 120 AU. Various clump density profiles, initial mass functions, protoplanetary disk models, stellar masses, and gap opening criteria are considered. When we use more realistic gap opening criteria, we find that gaps open only rarely which strongly affects clump survival rates and their physical properties (mass, radius and radial distance). The inferred surviving population is then shifted towards less massive clumps at smaller radial distances. We also find that populations of surviving clumps are very sensitive to the model assumptions and used parameters. Depending on the chosen parameters, the protoplanets occupy a mass range between 0.01 and 16 $M_{\text{J}}$ and may either orbit close to the central star or as far out as 75 AU, with a sweet spot at 10-30 AU for the massive ones. However, in all the cases we consider we find that massive giant planets at very large radial distances are rare in qualitative agreement with current direct imaging surveys. We conclude that caution should be taken in deriving population synthesis models as well as when comparing the models' results with observations.