OSSOS: The Eccentricity and Inclination Distributions of the Stable Neptunian Trojans

Abstract

The minor planets on orbits that are dynamically stable in Neptune's 1:1 resonance on Gyr timescales were likely emplaced by Neptune's outward migration. We explore the intrinsic libration amplitude, eccentricity, and inclination distribution of Neptune's stable Trojans, using the detections and survey efficiency of the Outer Solar System Origins Survey (OSSOS) and Pan-STARRS1. We find that the libration amplitude of the stable Neptunian Trojan population can be well modeled as a Rayleigh distribution with a libration amplitude width ${\sigma }_{A_{p}hi}$ of 15${}^{\circ }$. When taken as a whole, the Neptune Trojan population can be acceptably modeled with a Rayleigh eccentricity distribution of width ${\sigma }_e$ of 0.045 and a typical sin(i) x Gaussian inclination distribution with a width ${\sigma }_i$ of 14 +/- 2 degrees. However, these distributions are only marginally acceptable. This is likely because, even after accounting for survey detection biases, the known large Hr < 8 and small Hr >= 8 Neptune Trojans appear to have markedly different eccentricities and inclinations. We propose that like the classical Kuiper belt, the stable intrinsic Neptunian Trojan population have dynamically `hot' and dynamically `cold' components to its eccentricity/inclination distribution, with ${\sigma }_{e-cold}$ ~ 0.02 / ${\sigma }_{i-cold}$ ~ 6${}^{\circ }$ and ${\sigma }_{e-hot}$~ 0.05 / ${\sigma }_{i-hot}$ ~ 18${}^{\circ }$. In this scenario, the `cold' L4 Neptunian Trojan population lacks the Hr >= 8 members and has 13 +11/-6 `cold' Trojans with Hr < 8. On the other hand, the `hot' L4 Neptunian Trojan population has 136 +57/-48 Trojans with Hr < 10 -- a population 2.4 times greater than that of the L4 Jovian Trojans in the same luminosity range.

15 pages, 7 figures, v3, accepted for publication in Icarus

References in corpus (11)

• OSSOS VI. Striking Biases in the detection of large semimajor axis Trans-Neptunian Objects
• A Possible Divot in the Size Distribution of the Kuiper Belt's Scattering Objects
• Discovery of A New Retrograde Trans-Neptunian Object: Hint of A Common Orbital Plane for Low Semi-Major Axis, High Inclination TNOs and Centaurs
• Is the Missing Ultra-Red Material Colorless Ice?
• 2001 QR322: a dynamically unstable Neptune Trojan?
• The Intrinsic Neptune Trojan Orbit Distribution: Implications for the Primordial Disk and Planet Migration
• The Trojan Color Conundrum
• The 5:1 Neptune Resonance as Probed by CFEPS: Dynamics and Population
• Dynamical Classification of Trans-Neptunian Objects Detected by the Dark Energy Survey
• OSSOS XVIII: Constraining migration models with the 2:1 resonance using the Outer Solar System Origins Survey
• The Pan-STARRS 1 Discoveries of five new Neptune Trojans

Cited by in corpus (3)

• Tuning the Legacy Survey of Space and Time (LSST) Observing Strategy for Solar System Science
• Keck, Gemini, and Palomar 200-inch visible photometry of red and very-red Neptunian Trojans
• OSSOS: XXVII. Population Estimates for Theoretically Stable Centaurs Between Uranus and Neptune