Three-dimensional circumplanetary flows in a PDS 70c-inspired system: hydrodynamic simulations with FARGO3D and analysis with FARGOpy
The detection of circumplanetary material around the forming planet PDS~70c provides a valuable setting for studying three-dimensional gas accretion during giant-planet formation. We present three-dimensional hydrodynamic simulations with FARGO3D for a locally isothermal protoplanetary disk, adopting system-motivated stellar, orbital, and disk parameters and planetary masses of $2$, $4$, and $8,M_{\rm Jup}$, all above the local thermal mass. The locally isothermal prescription provides a controlled prescribed-temperature limit that isolates the hydrodynamic organization of the flow, without modeling self-consistent thermal evolution or radiative observables. Gas enters the planetary environment through meridional flows from the upper disk layers and streams near the midplane. With increasing planetary mass, the flow changes from a vertically extended, envelope-like configuration to a more compact and stratified circumplanetary structure. The inferred CPD radius increases from $R_{\rm CPD}\simeq0.31$ to $0.40,R_{\rm Hill}$, while the flow remains sub-Keplerian, reaching $v_ϕ/V_{K,p}\sim0.79$--$0.85$. Most enclosed gas mass lies within a few tenths of the Hill radius, whereas the outer Hill sphere is dominated by anisotropic inflow, outflow, and recirculation. The analysis was performed with FARGOpy, a Python post-processing framework developed in this work to reconstruct three-dimensional fields, compute integrated fluxes, and characterize circumplanetary kinematics from FARGO3D outputs. This study therefore provides both a hydrodynamic baseline for a PDS~70c-like environment and a reproducible framework for analyzing three-dimensional FARGO3D simulations.