PRIMASS visits Hilda and Cybele groups

TL;DR

This study analyzes the composition of Cybele and Hilda asteroid groups using spectroscopic data, revealing a continuous compositional distribution across the asteroid belt and identifying a unique Trojan population.

Contribution

It provides new spectroscopic observations and a comprehensive compositional analysis of Cybele and Hilda groups, expanding the understanding of their diversity and relation to other asteroid populations.

Findings

Continuous compositional distribution from main belt to Trojans

Identification of a unique Trojan population

Spectroscopic evidence of aqueous alteration features

Abstract

The Cybele and Hilda dynamical groups delimit the outer edge of the asteroid belt. Their compositional distribution is a key element to constrain evolutionary models of the Solar System. In this paper, we present a compositional analysis of these populations using spectroscopic observations, SDSS and NEOWISE data. As part of the PRIMASS (Primitive Asteroids Spectroscopic Survey), we acquired visible spectra of 18 objects in Hilda or Cybele groups with the Goodman High Throughput Spectrometer at the 4.1m SOAR telescope and 20 near-IR spectra of Hilda objects with Near Infrared Camera Spectrograph at the 3.56m TNG. The sample is enlarged with spectra taken from the literature in order to increase our statistical analysis. The spectra were inspected for aqueous alteration bands and other spectral features that can be linked to compositional constraints. The analysis shows a continuous distribution of compositions from the main-belt to the Cybele, Hilda and Trojan regions. We also identify a population in the Trojans group not present in Hilda or Cybele objects.