The influence of planetesimal fragmentation on planet formation

Abstract

Context. The effects of planetesimal fragmentation on planet formation have been studied via various models on single embryos, and have therefore mostly neglected concurrent effects in the outer disk. They show that planetesimal fragmentation can either hinder or aid planet formation, due to the introduction of competing effects, namely speeding up accretion and depleting the feeding zone of forming planets. Aims. We investigate the influence of the collisional fragmentation of planetesimals on the planet formation process using a population synthesis approach. Our aim is to investigate its effects for a large set of initial conditions and also to explore the consequences on the formation of multiple embryos in the same disk. Methods. We ran global planet formation simulations including fragmentation, drift, and an improved ice line description. To do this we used a fragmentation model in our code. The initial conditions for the simulations that are informed by observations are varied to generate synthetic exoplanet populations. Results. Our synthetic populations show that depending on the typical size of solids generated in collisions, fragmentation in tandem with radial drift can either enhance or hinder planet formation. For larger fragments we see increased accretion throughout the populations especially beyond the ice line. However, the shorter drift timescale of smaller fragments, due to their stronger coupling to the gas, can hinder the formation process. Furthermore, beyond the ice line fragmentation promotes late growth when the damping by gas drag fades. Conclusions. Fragmentation significantly affects the planet formation process in various ways for all types of planets and warrants further investigation.