ner_tags: O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Software I-Software I-Software O O O O O B-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O B-Software I-Software O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O
tokens: as shown in the right panel of Figure 2 . A power-law index of −0.6 clearly agrees with the mass function slope for low-mass objects. This suggests that the differential mass functions are well fit by a single power law because there is a significantly larger number of planetesimals at small masses, thus weighting the fit toward the small-mass end. Therefore, while in reality the mass distribution will have a cutoff at some high-mass value (which depends on τ ), the differential distribution can be well fit by a single power law that is representative of masses away from the cutoff. Finally, we have also examined the evolution of p and the maximum and minimum planetesimal masses (in all three simulations) for times after which a significant number of planetesimals have formed; the results are shown in Figure 3 . Note that due to limitations with the clump finder algorithm (as described more fully in Simon et al. 2016 ), we smoothed the curves (with a boxcar average) to remove noise associated with this algorithm. As the figure shows, p and the minimum planetesimal mass are relatively constant in time, 7 7 We do observe a slight decrease in the minimum mass in some instances, a behavior that could arise from a combination of processes, including tidal stripping of smaller bodies by large planetesimals, fragmentation of smaller bodies, and/or the preferential production of smaller planetesimals as the reservoir of particles from which to produce planetesimals decreases in size (Johansen et al. 2015 ). Elucidating the nature of this behavior requires a more sophisticated clump-finding algorithm and will thus be reserved for future work. whereas the maximum planetesimal mass grows by a factor of order unity in each simulation, likely due to accretion of smaller particles and/or mergers with smaller planetesimals. Despite this growth, the mass function does not evolve appreciably once planetesimals have formed. Figure 3. Time evolution of the power-law index (solid black line), maximum planetesimal mass (dashed red line), and minimum planetesimal mass (dotted blue line) for the (left), (middle), and (right) simulations for a period of time after planetesimals have formed. Both the power-law index, p , and the minimum planetesimal mass are relatively constant in time, whereas the maximum planetesimal mass grows slowly, presumably due to continued accretion of small particles and/or mergers with smaller planetesimals. Our ability to directly measure any potential dependence of the mass function on particle properties is limited by the relatively small number of collapsed clumps, but across the range of τ considered, we can bound deviations at the level of . We can therefore exclude, with moderately high confidence, the possibility that the streaming instability might result in a steep mass function () with most of the mass in the smallest planetesimals. 4. Particle Clustering Prior to Collapse The similarity in the mass functions from the different