Constraining giant planet formation with synthetic ALMA images of the Solar System's natal protoplanetary disk

TL;DR

This study uses synthetic ALMA images from simulations to explore how giant planets influence protoplanetary disk features, revealing complexities in interpreting observed disk structures and implications for planet formation scenarios.

Contribution

It demonstrates that multiple giant planets create observable traffic jams in disks, complicating the link between disk features and planet count, and highlights the importance of high-resolution observations for understanding planet formation.

Findings

Traffic jams caused by giant planets create observable over-densities.

Number of gaps and rings does not directly indicate the number of planets.

Dust mass estimates can be significantly off due to optical thickness.

Abstract

New ALMA observations of protoplanetary disks allow us to probe planet formation in other systems, giving us new constraints on planet formation processes. Meanwhile, studies of our own Solar System rely on constraints derived in a completely different way. However, it is still unclear what features the Solar System's disk could have produced during its gas phase. By running 2D isothermal hydro-simulations and a dust evolution model, we derive synthetic images at 1.3 mm wavelength using the radiative transfer code RADMC3D. We find that the embedded multiple giant planets strongly perturb the radial gas velocities of the disk, creating traffic jams in the dust. They produce over-densities different from the ones created by pressure traps and located away from the planets' positions in the disk. By deriving the images at 1.3mm from these dust distributions, we show that the traffic jams, observable with a high resolution, further blur the link between the number of gaps and rings in disks and the number of embedded planets. We additionally show that a system of 3 compact giant planets does not automatically produce bright outer rings at large radii in the disk. This means that high resolution observations of disks of various sizes are needed to distinguish between different giant planet formation scenarios during the disk phase, where the giants form either in the outer regions of the disks or in the inner regions. Finally, we find that, even when the dust temperature is determined self-consistently, the dust masses derived observationally might be off by up to a factor of ten compared to the dust contained in our simulations due to the creation of optically thick regions. Our study clearly shows that in addition to the constraints from exoplanets and the Solar System, ALMA has the power to constrain different stages of planet formation already during the first few million years.