Evidence for Universality in the Initial Planetesimal Mass Function
Abstract
Planetesimals may form from the gravitational collapse of dense particle clumps initiated by the streaming instability. We use simulations of aerodynamically coupled gasparticle mixtures to investigate whether the properties of planetesimals formed in this way depend upon the sizes of the particles that participate in the instability. Based on three highresolution simulations that span a range of dimensionless stopping times 6× {10}^{3}≤slant τ ≤slant 2, no statistically significant differences in the initial planetesimal mass function are found. The mass functions are fit by a power law, {dN}/{{dM}}_{p}\propto {M}_{p}^{p}, with p = 1.51.7 and errors of {{Δ }}p≈ 0.1. Comparing the particle density fields prior to collapse, we find that the highwavenumber power spectra are similarly indistinguishable, though the largescale geometry of structures induced via the streaming instability is significantly different between all three cases. We interpret the results as evidence for a nearuniversal slope to the mass function, arising from the smallscale structure of streaminginduced turbulence.
 Publication:

The Astrophysical Journal
 Pub Date:
 October 2017
 DOI:
 10.3847/20418213/aa8c79
 arXiv:
 arXiv:1705.03889
 Bibcode:
 2017ApJ...847L..12S
 Keywords:

 hydrodynamics;
 instabilities;
 planets and satellites: formation;
 Astrophysics  Earth and Planetary Astrophysics
 EPrint:
 7 pages, 4 figures, accepted to ApJ Letters after minor modifications, including two new figures and some new text that better clarify our results