Col-OSSOS: Probing Ice Line/Color Transitions within the Kuiper Belt's Progenitor Populations

TL;DR

This study investigates the radial distribution of surface colors in the Kuiper belt's progenitor populations, linking observed color bimodality to ice line positions during early solar system evolution.

Contribution

It combines dynamical modeling with observed surface colors to constrain the location of ice line/color transitions in the primordial Kuiper belt.

Findings

Color transition likely at 27-28 au from the Sun.

Both proposed initial color layouts are consistent with current observations.

The results refine understanding of Kuiper belt formation and composition.

Abstract

Dynamically excited objects within the Kuiper belt show a bimodal distribution in their surface colors, and these differing surface colors may be a tracer of where these objects formed. In this work we explore radial color distributions in the primordial planetesimal disk and implications for the positions of ice line/color transitions within the Kuiper belt's progenitor populations. We combine a full dynamical model of the Kuiper belt's evolution due to Neptune's migration with precise surface colors measured by the Colours of the Outer Solar System Origins Survey in order to examine the true color ratios within the Kuiper belt and the ice lines within the primordial disk. We investigate the position of a dominant, surface color changing ice-line, with two possible surface color layouts within the initial disk; (1) inner neutral surfaces and outer red, and (2) inner red surfaces and outer neutral. We performed simulations with a primordial disk that truncates at 30 au. By radially stepping the color transition out through 0.5 au intervals we show that both disk configurations are consistent with the observed color fraction. For an inner neutral, outer red primordial disk we find that the color transition can be at $28^{+2}_{-3}$ au at a 95% confidence level. For an inner red, outer neutral primordial disk the color transition can be at $27^{+3}_{-3}$ au at a 95% confidence level.