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 _ { \phi } } of 15 \degr .
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 ) \times gaussian inclination distribution with a width { \sigma _ { i } } of 14 \pm 2 ^ { \circ } ; however , these distributions are only marginally acceptable .
This is likely because , even after accounting for survey detection biases , the known large ( H _ { r } < 8 ) and small ( H _ { r } \geq 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 } \sim 0.02 / \sigma _ { i - cold } \sim 6 ^ { \circ } and \sigma _ { e - hot } \sim 0.05 / \sigma _ { i - hot } \sim 18 ^ { \circ } .
In this scenario , the ‘ cold ’ L4 Neptunian Trojan population lacks the H _ { r } \geq 8.0 member and has 13 ^ { +11 } _ { -6 } ‘ cold ’ Trojans with H _ { r } < 8.0 .
On the other hand , the ‘ hot ’ L4 Neptunian Trojan population has 136 ^ { +57 } _ { -48 } Trojans with H _ { r } < 10 — a population 2.4 times greater than that of the L4 Jovian Trojans in the same luminosity range .