Modeling the Architecture and Water Content of Exoplanet Systems by Pebble Accretion: The PPOLS Model

Abstract

A key area linking frontier observational capabilities to theoretical questions of exoplanet system architectures is the transport and evolution of water in planet-forming disks and mechanisms that tune its incorporation into planets. This research develops a pebble accretion model of planet formation (“the PPOLs Model”) that self-consistently handles the drift and accretion of rocky/icy pebbles around stars ranging from late M-dwarfs to early A-stars. The model grows multiple protoplanet cores simultaneously and evolves the snow line position consistently with evolving disk conditions. The combination of growing multiple cores while evolving the snowline allows for a prolonged period of growth and delivery of icy pebbles to the inner disk. For a narrow range of disk mass parameters around solar-mass stars, an “Earth-like” amount of water is delivered to ~Earth mass planets in the conservative habitable zone. Overall, a distinct trend in the water content is seen for a narrow range of disk masses across all stellar masses tested. Ultimately, the outputs of the PPOLs model do not align with previously recorded simulations of the late-stage phase of planet formation in the genesis model, indicating the importance of outer disk influence in determining exoplanet system architectures.