Color and Size Distributions of Small Jupiter Trojans

TL;DR

This study used Subaru Telescope imaging to analyze the color and size distributions of small Jupiter Trojans, revealing a lack of bimodality in their colors and similar size distributions across color groups, informing their collisional evolution.

Contribution

It provides the first detailed analysis of small Jupiter Trojans' color and size distributions, showing the absence of bimodality and similar size distributions across color groups, which advances understanding of their collisional history.

Findings

No bimodality in color distribution for small Trojans.

Size distributions are similar across different color groups.

Results suggest specific collisional evolution processes.

Abstract

We conducted a two-band imaging survey observation using the Subaru Telescope and its wide-field camera, Suprime-Cam, to study the visible colors and size distribution of Jupiter's Trojan asteroids. The survey covered an area around Jupiter's L4 Lagrange point totaling 9.2 square degrees. We detected 120 Trojan asteroids in this survey. From these Trojan asteroids, we extracted 44 unbiased samples with absolute magnitudes in the $g^\prime$ band ranging from 12.9 to 16.9 mag (corresponding to diameter ranges of approximately $\sim$3 - 16 km assuming an albedo of 0.05) and analyzed their $g^\prime - i^\prime$ color and size distributions. Large Jupiter Trojan asteroids are known to be classified into two color groups, ''red'' and ''less red''. We found that such bimodality in the color distribution is absent for small Jupiter Trojan asteroids, which is consistent with previous studies. Previous studies have also shown that these two groups have different slopes in the magnitude distributions from each other, which was explained by conversion of red objects to less-red fragments through catastrophic disruptions. In contrast, we found that the size frequency distributions of our two sample groups divided by the color of $g^\prime - i^\prime$ = 0.7 (in AB magnitude) are quite similar. Our results can provide new insights into collisional evolution of color and size distribution of small Jupiter Trojans.