The Mass and Size Distribution of Planetesimals Formed by the Streaming Instability. I. The Role of Selfgravity
Abstract
We study the formation of planetesimals in protoplanetary disks from the gravitational collapse of solid overdensities generated via the streaming instability. To carry out these studies, we implement and test a particlemesh selfgravity module for the Athena code that enables the simulation of aerodynamically coupled systems of gas and collisionless selfgravitating solid particles. Upon employment of our algorithm to planetesimal formation simulations, we find that (when a direct comparison is possible) the Athena simulations yield predicted planetesimal properties that agree well with those found in prior work using different numerical techniques. In particular, the gravitational collapse of streaminginitiated clumps leads to an initial planetesimal mass function that is wellrepresented by a power law, {dN}/{{dM}}_{p}\propto {M}_{p}^{p}, with p≃ 1.6+/ 0.1, which equates to a differential size distribution of {dN}/{{dR}}_{p}\propto {R}_{p}^{q}, with q≃ 2.8+/ 0.1. We find no significant trends with resolution from a convergence study of up to 512^{3} grid zones and {N}_{{{par}}}≈ 1.5× {10}^{8} particles. Likewise, the powerlaw slope appears indifferent to changes in the relative strength of selfgravity and tidal shear, and to the time when (for reasons of numerical economy) selfgravity is turned on, though the strength of these claims is limited by small number statistics. For a typically assumed radial distribution of minimum mass solar nebula solids (assumed here to have dimensionless stopping time τ =0.3), our results support the hypothesis that bodies on the scale of large asteroids or Kuiper Belt Objects could have formed as the highmass tail of a primordial planetesimal population.
 Publication:

The Astrophysical Journal
 Pub Date:
 May 2016
 DOI:
 10.3847/0004637X/822/1/55
 arXiv:
 arXiv:1512.00009
 Bibcode:
 2016ApJ...822...55S
 Keywords:

 hydrodynamics;
 instabilities;
 planets and satellites: formation;
 protoplanetary disks;
 Astrophysics  Solar and Stellar Astrophysics;
 Astrophysics  Earth and Planetary Astrophysics
 EPrint:
 18 pages, 16 figures, accepted to ApJ after minor revisions and title change