Col-OSSOS: The Distribution of Surface Classes in Neptune's Resonances

TL;DR

This study classifies TNO surfaces into BrightIR and FaintIR types using multi-band photometry, revealing their distribution in Neptune's resonances and implications for planetary migration and disk evolution.

Contribution

It introduces a two-class surface classification for TNOs based on spectral slopes and analyzes their distribution across Neptune's resonances, informing models of planetary migration.

Findings

FaintIR surfaces are prevalent in cold classical TNOs.

The 3:2 resonance has minimal FaintIR objects, likely due to secular resonance clearing.

FaintIR objects in other resonances suggest formation between 34.6 and 47 au.

Abstract

The distribution of surface classes of resonant trans-Neptunian objects (TNOs) provides constraints on the protoplanetesimal disk and giant planet migration. To better understand the surfaces of TNOs, the Colours of the Outer Solar System Origins Survey (Col-OSSOS) acquired multi-band photometry of 102 TNOs, and found that the surfaces of TNOs can be well described by two surface classifications, BrightIR and FaintIR. These classifications both include optically red members and are differentiated predominantly based on whether their near-infrared spectral slope is similar to their optical spectral slope. The vast majority of cold classical TNOs, with dynamically quiescent orbits, have the FaintIR surface classification, and we infer that TNOs in other dynamical classifications with FaintIR surfaces share a common origin with the cold classical TNOs. Comparison between the resonant populations and the possible parent populations of cold classical and dynamically excited TNOs reveal that the 3:2 has minimal contributions from the FaintIR class, which could be explained by the $\nu_8$ secular resonance clearing the region near the 3:2 before any sweeping capture occurred. Conversely, the fraction of FaintIR objects in the 4:3 resonance, 2:1 resonance, and the resonances within the cold classical belt, suggest that the FaintIR surface formed in the protoplanetary disk between 34.6 and 47 au, though the outer bound depends on the degree of resonance sweeping during migration. The presence and absence of the FaintIR surfaces in Neptune's resonances provides critical constraints for the history of Neptune's migration, the evolution of the $\nu_8$, and the surface class distribution in the initial planetesimal disk