OSSOS. VIII. The Transition between Two Size Distribution Slopes in the Scattering Disk

Abstract

The scattering trans-Neptunian Objects (TNOs) can be measured to smaller sizes than any other distant small-body population. We use the largest sample yet obtained, 68 discoveries, primarily by the Outer Solar System Origins Survey (OSSOS), to constrain the slope of its luminosity distribution, with sensitivity to much fainter absolute H-magnitudes than previous work. Using the analysis technique in Shankman et al., we confirm that a single slope for the H-distribution is not an accurate representation of the scattering TNOs and Centaurs, and that a break in the distribution is required, in support of previous conclusions. A bright-end slope of alpha(b) = 0.9 transitioning to a faint-end slope alpha(f) of 0.4-0.5 with a differential number contrast c from 1 (a knee) to 10 (a divot) provides an acceptable match to our data. We find that break magnitudes H-b of 7.7 and 8.3, values both previously suggested for dynamically hot Kuiper Belt populations, are equally non-rejectable for a range of alpha(f) and c in our statistical analysis. Our preferred divot H-distribution transitions to alpha(f) = 0.5 with a divot of contrast c = 3 at H-b = 8.3, while our preferred knee H-distribution transitions to alpha(f) = 0.4 at H-b = 7.7. The intrinsic population of scattering TNOs required to match the OSSOS detections is 3 x 10(6) for H-r < 12, and 9 x 10(4) for H-r < 8.66 (D greater than or similar to 100 km), with Centaurs having an intrinsic population two orders of magnitude smaller.