exoALMA. VII. Benchmarking hydrodynamics and radiative transfer codes

Forward modeling is often used to interpret substructures observed in protoplanetary disks. To ensure the robustness and consistency of the current forward-modeling approach from the community, we conducted a systematic comparison of various hydrodynamics and radiative transfer codes. Using four grid-based hydrodynamics codes (FARGO3D, Idefix, Athena++, and PLUTO) and a smoothed-particle hydrodynamics code (Phantom), we simulated a protoplanetary disk with an embedded giant planet. We then used two radiative transfer codes (mcfost and RADMC-3D) to calculate disk temperatures and create synthetic ¹²CO cubes. Finally, we retrieved the location of the planet from the synthetic cubes using DISCMINER. We found strong consistency between the hydrodynamics codes, particularly in the density and velocity perturbations associated with planet-driven spirals. We also found a good agreement between the two radiative transfer codes: the disk temperature in mcfost and RADMC-3D models agrees within ≲3% everywhere in the domain. In synthetic ¹²CO channel maps, this results in brightness temperature differences within ±1.5 K in all our models. This good agreement ensures consistent retrieval of planet’s radial/azimuthal location with only a few percent of scatter, with velocity perturbations varying ≲20% among the models. Notably, while the planet-opened gap is shallower in the Phantom simulation, we found that this does not impact the planet location retrieval. In summary, our results demonstrate that any combination of the tested hydrodynamics and radiative transfer codes can be used to reliably model and interpret planet-driven kinematic perturbations.