The Resonant Transneptunian Populations

TL;DR

This study models transneptunian objects in various Neptune resonances, refining population estimates, orbital distributions, and revealing discrepancies with existing models, thereby enhancing understanding of the Kuiper Belt's structure and formation history.

Contribution

It provides new population estimates and orbital distribution constraints for multiple Neptune resonances, and compares these with theoretical models, highlighting significant discrepancies.

Findings

Refined orbital element distribution for plutinos in the 3:2 resonance.

First population estimate for the 5:2 resonance, comparable to the 3:2.

Resonances beyond 2:1 are more populated than current models predict.

Abstract

The transneptunian objects (TNOs) trapped in mean-motion resonances with Neptune were likely emplaced there during planet migration late in the giant-planet formation process. We perform detailed modelling of the resonant objects detected in the Canada-France Ecliptic Plane Survey (CFEPS) in order to provide population estimates and, for some resonances, constrain the complex internal orbital element distribution. Detection biases play a critical role because phase relationships with Neptune make object discovery more likely at certain longitudes. This paper discusses the 3:2, 5:2, 2:1, 3:1, 5:1, 4:3, 5:3, 7:3, 5:4, and 7:4 mean-motion resonances, all of which had CFEPS detections, along with our upper limit on 1:1 Neptune Trojans (which is consistent with their small population estimated elsewhere). For the plutinos (TNOs in the 3:2 resonance) we refine the orbital element distribution given in Kavelaars et al. (2009) and show that steep H-magnitude distributions (N(H) proportional to 10aH, with a=0.8-0.9) are favoured in the range Hg=8-9, and confirm that this resonance does not share the inclination distribution of the classical Kuiper Belt. We give the first population estimate for the 5:2 resonance and find that, to within the uncertainties, the population is equal to that of the 3:2 (13,000 TNOs with Hg < 9.16), whereas the 2:1 population is smaller by a factor of 3-4 compared to the other two resonances. We also measure significant populations inhabiting the 4:3, 5:3, 7:3, 5:4, 7:4, 3:1, and 5:1 resonances, with Hg < 9.16 (D >100 km) populations in the thousands. We compare our intrinsic population and orbital-element distributions with several published models of resonant-TNO production; the most striking discrepancy is that resonances beyond the 2:1 are in reality more heavily populated than in published models.