The differing magnitude distributions of the two Jupiter Trojan color populations

TL;DR

This study reveals that the two color populations of Jupiter Trojans have distinct magnitude distributions, suggesting they formed in different locations and have different evolutionary histories.

Contribution

The paper provides a detailed analysis of the magnitude distributions of the two color populations, demonstrating their statistical differences and implications for Trojan origins.

Findings

Red and less red Trojans have different faint-end slopes.

The two populations' magnitude distributions are statistically distinct.

Results support different formation locations for the two groups.

Abstract

The Jupiter Trojans are a significant population of minor bodies in the middle Solar System that have garnered substantial interest in recent years. Several spectroscopic studies of these objects have revealed notable bimodalities with respect to near-infrared spectra, infrared albedo, and color, which suggest the existence of two distinct groups among the Trojan population. In this paper, we analyze the magnitude distributions of these two groups, which we refer to as the red and less red color populations. By compiling spectral and photometric data from several previous works, we show that the observed bimodalities are self-consistent and categorize 221 of the 842 Trojans with absolute magnitudes in the range H<12.3 into the two color populations. We demonstrate that the magnitude distributions of the two color populations are distinct to a high confidence level (>95%) and fit them individually to a broken power law, with special attention given to evaluating and correcting for incompleteness in the Trojan catalog as well as incompleteness in our categorization of objects. A comparison of the best-fit curves shows that the faint-end power-law slopes are markedly different for the two color populations, which indicates that the red and less red Trojans likely formed in different locations. We propose a few hypotheses for the origin and evolution of the Trojan population based on the analyzed data.