Feeding the Circumplanetary Disk: 3D Simulations of Dust Filtration and Accretion in PDS 70 c

Abstract

How circumplanetary disks (CPDs) capture and retain solids is central to constraining the timescale for formation of rocky satellites and interpreting submillimeter continuum observations around giant planets. Here, we investigate the transport of gas and dust from the circumstellar disk into the CPD, using PDS 70 as our fiducial example. Based on observation-driven parameters, we perform high-resolution 3D adaptive mesh refinement (AMR) hydrodynamic simulations including a multifluid dust component to study dust accretion onto planets with masses of 1 $M_\mathrm{J}$ and 2.5 $M_\mathrm{J}$. We find that the pressure maximum at the gap edge imposes strong, size-dependent dust filtration, drastically lowering the solid content of the accreting flow. The net dust-to-gas mass ratio of the material accreting onto the planet is reduced by roughly two orders of magnitude relative to the outer disk. Only small grains ($\lesssim 61 μ$m for the 1 $M_\mathrm{J}$ case and $\lesssim 10 μ$m for the 2.5 $M_\mathrm{J}$ case) are able to accrete efficiently onto the CPD. Despite this filtering, we show that a continuous inflow of small grains can still deliver sufficient mass to build the observed PDS 70 c CPD or a Galilean-like satellite system within a few million years. Because more massive planets more effectively prevent the accretion of large grains, the dust that reaches the CPD is dominated by small particles with low millimeter-wave opacities. Consequently, in the absence of grain growth, interpreting millimeter continuum measurements of CPDs around massive giant planets may require invoking larger total dust masses than typically assumed.