The influence of planetesimal fragmentation on planet formation

Nicolas Leo Kaufmann

Context. The effects of planetesimal fragmentation on planet formation has been studied by various models on single embryos
therefore neglecting concurrent effects mostly in the outer disk. They show that planetesimal fragmentation can both hinder or aid
planet formation due to the introduction of competing effects, namely speeding up accretion and depleting the feeding zone of forming
Aims. We investigate the influence of the collisional fragmentation of planetesimals on the planet formation process using a population
synthesis approach. We aim to investigate its effects for a large set of initial conditions and also explore the consequences on the
formation of multiple embryos in the same disk.
Methods. We run global planet formation simulations including fragmentation, drift and an improved ice line description. To do this
we use a fragmentation model based on Ormel & Kobayashi (2012) into 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 the 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 planet and warrants
further investigation.