Size Distribution of Small Hilda Asteroids

TL;DR

This study analyzes the size distribution of small Hilda asteroids using Subaru Telescope data, revealing a power-law distribution and similarities with Jupiter Trojans, suggesting a shared origin.

Contribution

First detailed size distribution analysis of small Hilda asteroids down to 1 km diameter using optical survey data.

Findings

Hildas' size distribution follows a single-slope power law with slope 0.38.

Hildas and Jupiter Trojans have similar size distributions below 10 km.

Hildas are less numerous than Jupiter Trojans by a factor of five.

Abstract

We present the size distribution for Hilda asteroid group using optical survey data obtained by the 8.2 m Subaru Telescope with the Hyper Suprime-Cam. Our unbiased sample consists of 91 Hilda asteroids (Hildas) down to 1~km in diameter. We found that the Hildas' size distribution can be approximated by a single-slope power law in the ~1-10 km diameter range with the best-fit power-law slope of alpha = 0.38 +/- 0.02 in the differential absolute magnitude distribution. Direct comparing the size distribution of Hildas with that of the Jupiter Trojans measured from the same dataset Yoshida & Terai (2017) indicates that the two size distributions are well similar to each other within a diameter of ~10 km, while these shapes are distinguishable from that of main-belt asteroids. The results suggest that Hildas and Jupiter Trojans share a common origin and have a different formation environment from main-belt asteroids. The total number of the Hilda population larger than 2 km in diameter is estimated to be ~1 x 10^4 based on the size distribution, which is less than that of the Jupiter Trojan population by a factor of about five.