The Mass Budgets and Spatial Scales of Exoplanet Systems and Protoplanetary Disks

TL;DR

This study compares the mass and size of solid material in protoplanetary disks and exoplanet systems, revealing that observational biases and formation efficiency influence perceived discrepancies, and suggesting disk properties impact exoplanet characteristics.

Contribution

It provides a comprehensive analysis linking disk properties to exoplanet system features, accounting for observational biases and proposing a correlation between disk size and planetary system mass.

Findings

Discrepancy in dust mass disappears when considering detection biases.

Positive correlation between planetary system mass and orbital period.

Disk properties appear to influence exoplanet system characteristics.

Abstract

Planets are born from disks of gas and dust, and observations of protoplanetary disks are used to constrain the initial conditions of planet formation. However, dust mass measurements of Class II disks with ALMA have called into question whether they contain enough solids to build the exoplanets that have been detected to date. In this paper, we calculate the mass and spatial scale of solid material around Sun-like stars probed by transit and radial velocity exoplanet surveys, and compare those to the observed dust masses and sizes of Class II disks in the same stellar mass regime. We show that the apparent mass discrepancy disappears when accounting for observational selection and detection biases. We find a discrepancy only when the planet formation efficiency is below 100%, or if there is a population of undetected exoplanets that significantly contributes to the mass in solids. We identify a positive correlation between the masses of planetary systems and their respective orbital periods, which is consistent with the trend between the masses and the outer radii of Class II dust disks. This implies that, despite a factor 100 difference in spatial scale, the properties of protoplanetary disks seem to be imprinted on the exoplanet population.