A giant solution to the disk mass budget problem of planet formation

TL;DR

This paper investigates the dust mass budget problem in planet formation by analyzing dust evolution in protoplanetary disks, highlighting the role of pressure bumps and planetesimal formation in dust depletion.

Contribution

It extends previous analysis by separating dust mass distributions at different stages and identifies conditions that best match observed disk masses, emphasizing the impact of pressure bumps and planetesimal formation.

Findings

Disks with initial masses of 4-7% solar mass best match observations.

Pressure bumps from giant planets can facilitate planetesimal formation.

Dust masses in models remain higher than observed in evolved disks.

Abstract

Understanding how dust evolves in protoplanetary disks is crucial to constraining the initial conditions of planet formation. The apparent "mass budget problem", which stems from the comparison of the observed disk masses to the ones inferred for exoplanets, remains debated, as it is unclear whether the discrepancy arises from limitations in interpreting disk observations, from evolutionary processes that rapidly deplete dust, or from incorrect assumptions about the initial disk mass distribution. This work is build on the analysis presented in Savvidou and Bitsch (2025) by separating the cumulative distribution functions of dust masses at different evolutionary stages into different populations according to the initial disk masses and embryo injection times. The best match to observations comes from disks with intermediate initial disk masses around 4-7% solar mass. The largest discrepancy between the total dust mass in the models and the estimated through an "optically thin" approximation comes from the models that have the most favorable conditions for giant planet formation and thus contain a large fraction of giants and subsequently trapped "optically thick" dust mass because of the pressure bumps they generate. However, the final dust masses remain higher compared to the estimates from the observed evolved disks. Example cases in this work including planetesimal formation show that the pressure bumps that giant planets form can be prime locations for planetesimal formation and the conversion to planetesimals significantly decreases the dust mass, as expected. However, (giant) planet formation is not influenced showing that the mass in evolved protoplanetary disks can be estimated to be quite low but it can be a natural consequence of planetesimal and planet formation along with depletion due to radial drift.