Circumplanetary Disk Dynamics in the Isothermal and Adiabatic Limits
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Circumplanetary disks (CPDs) may be essential to the formation of planets, regulating their spin and accretion evolution. We perform a series of 3D hydrodynamics simulations in both the isothermal and adiabatic limits to systematically measure the rotation rates, sizes, and masses of CPDs as functions of qthermal, the ratio of the planet mass to the disk thermal mass. Our qthermal ranges from 0.1 to 4; for our various disk temperatures, this corresponds to planet masses between one Earth mass and four Jupiter masses. Within this parameter space, we find that isothermal CPDs are disky and bound within ~10% of the planet's Bondi radius rB, with the innermost ~0.05rB in full rotational support. Adiabatic CPDs are spherical (and therefore not actually "disks"), bound within ~0.2rB, and mainly pressure-supported, with rotation rates scaling linearly with qthermal extrapolation suggests full rotational support of adiabatic envelopes at ~10 qthermal. Fast rotation and 3D supersonic flow render isothermal CPDs significantly different in structure from—and orders of magnitude less massive than—their 1D isothermal hydrostatic counterparts. Inside a minimum-mass solar nebula, even a maximally cooled, isothermal CPD around a 10 Earth-mass core may have less than one Earth mass, suggesting that gas giant formation may hinge on angular momentum transport processes in CPDs. Our CPD sizes and masses appear consistent with the regular satellites orbiting solar system giants.
Astrophysics and Astronomy | Physical Processes
Circumplanetary Disk Dynamics in the Isothermal and Adiabatic Limits.
Astrophysical Journal, 887(2),