There is no disk mass budget problem of planet formation

TL;DR

This paper uses numerical simulations to demonstrate that the apparent dust mass deficiency in protoplanetary disks does not hinder planet formation, as dust trapping and early formation can hide significant mass.

Contribution

It shows that dust trapping by planets and early formation stages resolve the apparent mass budget problem in planet formation.

Findings

Dust trapping prevents rapid dust mass loss.

Optically thin dust mass underestimates total dust mass.

Hidden dust mass can explain the mass budget problem.

Abstract

The inferred dust masses from Class II protoplanetary disk observations are lower than or equal to the masses of the observed exoplanet systems. This poses the question of how planets form if their natal environments do not contain enough mass. This hypothesis has entered the literature as the "mass budget problem" of planet formation. We utilize numerical simulations of planet formation via pebble and gas accretion, including migration, in a viscously evolving protoplanetary disk, while tracing the time evolution of the dust mass. As expected, we find that the presence of a giant planet in the disk can influence the evolution of the disk itself and prevent rapid dust mass loss by trapping the dust outside its orbit. Early formation is crucial for giant planet formation, as we found in our previous work; therefore, our findings strengthen the hypothesis that planet formation has already occurred or is ongoing in Class II disks. Most importantly, we find that the optically thin dust mass significantly underestimates the total dust mass in the presence of a dust-trapping deep gap. We also show that the beam convolution would smear out the feature from a deep gap, especially if the planet forms in the inner disk. Such hidden dust mass, along with early planet formation, could be the answer to the hypothetical mass budget problem.