The color-magnitude distribution of Hilda asteroids: Comparison with Jupiter Trojans

Abstract

Current models of Solar System evolution posit that the asteroid populations in resonance with Jupiter are comprised of objects scattered inward from the outer Solar System during a period of dynamical instability. In this paper, we present a new analysis of the absolute magnitude and optical color distribution of Hilda asteroids, which lie in the 3:2 mean motion resonance with Jupiter, with the goal of comparing the bulk properties with previously published results from an analogous study of Jupiter Trojans. We report an updated power law fit of the Hilda magnitude distribution through H=14. Using photometric data listed in the Sloan Moving Object Catalog, we confirm the previously-reported strong bimodality in visible spectral slope distribution, indicative of two sub-populations with differing surface compositions. When considering collisional families separately, we find that collisional fragments follow a unimodal color distribution with spectral slope values consistent with the bluer of the two sub-populations. The color distributions of Hildas and Trojans are comparable and consistent with a scenario in which the color bimodality in both populations developed prior to emplacement into their present-day locations. We propose that the shallower magnitude distribution of the Hildas is a result of an initially much larger Hilda population, which was subsequently depleted as smaller bodies were preferentially ejected from the narrow 3:2 resonance via collisions. Altogether, these observations provide a strong case supporting a common origin for Hildas and Trojans as predicted by current dynamical instability theories of Solar System evolution.

arXiv comment7 pages, 6 figures, accepted for publication in AJ

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• Zero-phase angle asteroid taxonomy classification using unsupervised machine learning algorithms
• Investigating the stability of mass transfer in neutron star-helium white dwarf binaries
• Size Distribution of Small Hilda Asteroids
• $0.7-2.5\mu$m spectra of Hilda asteroids
• Astrocladistics of the Jovian Trojan Swarms
• Photometric Confirmation and Characterization of the Ennomos Collisional Family in the Jupiter Trojans
• Collisional study of Hilda and quasi-Hilda asteroids
• On the forced orbital plane of the Hilda asteroids