The Two Modes of Gas Giant Planet Formation

Abstract

I argue for two modes of gas giant planet formation and discuss the conditions under which each mode operates. Gas giant planets at disk radii $r>100$ AU are likely to form in situ by disk instability, while core accretion plus gas capture remains the dominant formation mechanism for $r<100$ AU. During the mass accretion phase, mass loading can push disks toward fragmentation conditions at large $r$. Massive, extended disks can fragment into clumps of a few to tens of Jupiter masses. This is confirmed by radiation hydrodynamics simulations. The two modes of gas giant formation should lead to a bimodal distribution of gas giant semi-major axes. Because core accretion is expected to be less efficient in low-metallicity systems, the ratio of gas giants at large $r$ to planets at small $r$ should increase with decreasing metallicity.

Submitted to ApJL after addressing referee's comments

References in corpus (6)

• Optical Images of an Exosolar Planet 25 Light Years from Earth
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• Direct Imaging and Spectroscopy of a Planetary Mass Candidate Companion to a Young Solar Analog
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Cited by in corpus (2)

• The Effects of Radiative Transfer on Low-Mass Star Formation
• The applicability of the viscous α-parameterization of gravitational instability in circumstellar disks