3D Global Simulations of Accretion onto Gap-opening Planets: Implications for Circumplanetary Disc Structures and Accretion Rates

TL;DR

This study uses 3D simulations to analyze how giant planets accrete material from protoplanetary discs, revealing new insights into flow structures, accretion rates, and the importance of three-dimensional effects for understanding planet formation.

Contribution

The paper provides the first comprehensive 3D simulation analysis of accretion onto gap-opening planets, highlighting the flow dynamics, accretion scaling laws, and the necessity of 3D modeling for super-Jupiters.

Findings

Accretion mainly comes from intermediate latitudes above the disc midplane.

The circumplanetary disc is rotation-supported up to 20-30% of the Hill radius.

No accretion outburst from disc eccentricity was observed in 3D simulations.

Abstract

We perform a series of 3D simulations to study the accretion of giant planet embedded in protoplanetary discs (PPDs) over gap-opening timescales. We find that the accretion mass flux mainly comes from the intermediate latitude above the disc midplane. The circumplanetary disc (CPD) for a super-thermal planet is rotation-supported up to $\sim$20-30\% of the planet Hill radius. While both mass inflow and outflow exists in the CPD midplane, the overall trend is an outflow that forms a meridional circulation with high-latitude inflows. We confirm the absence of accretion outburst from disc eccentricity excited by massive planets in our 3D simulations, contrary to the consensus of previous 2D simulations. This suggests the necessity of 3D simulations of accretion even for super-Jupiters. The accretion rates of planets measured in steady-state can be decomposed into the ``geometric" and ``density depletion" factors. Through extensive parameter survey, we identify a power-law scaling for the geometric factor $\propto q_{\rm th}^{2/3}$ for super-thermal planets ($q_{\rm th}$ being the thermal mass ratio), which transforms to $\propto q_{\rm th}^{2}$ for less massive cases. The density depletion factor is limited by the disc accretion rate for mildly super-thermal planets, and by gap-opening for highly super-thermal ones. Moderate planetary eccentricities can enhance the accretion rates by a factor of $2-3$ through making the gap shallower, but does not impact the flow geometry. We have applied our simulations results to accreting protoplanet system PDS 70 and can satisfactorily explain the accretion rate and CPD size in observations.