Quantification of stochastic fragmentation of self-gravitating discs

TL;DR

This study analyzes the distribution of shock wait times in turbulent self-gravitating discs using SPH simulations, confirming previous models and assessing the likelihood of stochastic fragmentation affecting planet formation zones.

Contribution

It provides a detailed analysis of shock wait time distributions and evaluates the impact of stochastic fragmentation on the potential for planet formation.

Findings

Shock wait time distributions are consistent across different cooling times and resolutions.

Stochastic fragmentation cannot significantly alter the radius for disc fragmentation (~20%).

Direct gravitational collapse as a planet formation mechanism is limited to outer disc regions.

Abstract

Using 2D smoothed particle hydrodynamics, we investigate the distribution of wait times between strong shocks in a turbulent, self-gravitating accretion disc. We show the resulting distributions do not depend strongly on the cooling time or resolution of the disc and that they are consistent with the predictions of earlier work (Young & Clarke 2015; Cossins et al. 2009, 2010). We use the distribution of wait times between shocks to estimate the likelihood of stochastic fragmentation by gradual contraction of shear-resistant clumps on the cooling time scale. We conclude that the stochastic fragmentation mechanism (Paardekooper 2012) cannot change the radius at which fragmentation is possible by more than ~20%, restricting direct gravitational collapse as a mechanism for giant planet formation to the outer regions of protoplanetary discs.