Satellite Survival through Gas Redistribution in a Low-viscosity Disk

Abstract

We investigate satellite survival through gas redistribution in a dense circumplanetary disk with a low dimensionless viscosity parameter $α\sim 10^{-6}$. The model combines modal Lindblad excitation, launch-dependent shock deposition, 3D effects, and a conservative, instantaneous Rayleigh adjustment that prevents sharp gas density gradients. An isolated Ganymede-mass satellite depletes the disk outside its orbit and stalls, even in the presence of a calibrated three-dimensional Lindblad torque. This behavior is consistent with the non-feedback branch of Rafikov's stalling criterion. The inward migration stalls near 15 Jupiter radii ($R_J$) when the gas depletion exterior to the satellite's orbit reduces the outer torque by the amount required to balance the torque of the undepleted inner disk, even when we adopt a transport prescription to smooth out density gradients well before Rayleigh marginality is attained. Likewise, two Callisto masses form an extended depleted region (or gap) and stall in nearly steady orbits before a late close encounter. However, a self-consistent disk response to satellite eccentricity remains to be modeled. Lastly, a simulation of a single Ganymede-mass satellite with the same initial disk adds a specified analytical source of unsaturated local angular momentum deposition by buoyancy torques. By removing the gas pile-up at the satellite's location, this local deposition reduces the late radial oscillations caused by non-local shock deposition.