OSSOS. XXIX. The Population and Perihelion Distribution of the Detached Kuiper Belt

TL;DR

This study analyzes the distribution and population of detached Kuiper Belt objects using OSSOS data, revealing a non-uniform perihelion distribution and estimating around 50,000 such objects, supporting models involving early Solar System planetary perturbations.

Contribution

First to model the orbital distribution of detached TNOs using survey bias correction and compare with rogue planet simulations, providing new population estimates.

Findings

Detached TNO perihelion distribution is non-uniform with a break near 40 au.

Estimated total detached TNOs with D > 100 km is approximately 50,000.

Rogue planet models better match the observed perihelion distribution.

Abstract

The detached transneptunian objects (TNOs) are those with semimajor axes beyond the 2:1 resonance with Neptune, which are neither resonant nor scattering. Using the detached sample from the OSSOS telescopic survey, we produce the first studies of their orbital distribution based on matching the orbits and numbers of the known TNOs after accounting for survey biases. We show that the detached TNO perihelion ($q$) distribution cannot be uniform, but is instead better matched by two uniform components with a break near $q\approx40$ au. We produce parametric two-component models that are not rejectable by the OSSOS data set, and estimate that there are $36,\!000^{+12,000}_{-9,000}$ detached TNOs with absolute magnitudes $H_r < 8.66$ ($D \gtrsim 100$ km) and semimajor axes $48 < a < 250$ au (95% confidence limits). Although we believe these heuristic two-parameter models yield a correct population estimate, we then use the same methods to show that the perihelion distribution of a detached disk created by a simulated rogue planet matches the $q$ distribution even better, suggesting that the temporary presence of other planets in the early Solar System is a promising model to create today's large semimajor axis TNO population. This numerical model results in a detached TNO population estimate of $48,\!000^{+15,000}_{-12,000}$. Because this illustrates how difficult-to-detect $q>50$ au objects are likely present, we conclude that there are $(5 \pm 2)\times10^4$ dynamically detached TNOs, which are thus roughly twice as numerous as the entire transneptunian hot main belt.