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Photometric Confirmation and Characterization of the Ennomos Collisional Family in the Jupiter Trojans

Wong, Ian and Brown, Michael E. (2023) Photometric Confirmation and Characterization of the Ennomos Collisional Family in the Jupiter Trojans. Astronomical Journal, 165 (1). Art. No. 15. ISSN 0004-6256. doi:10.3847/1538-3881/ac9eb3.

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Collisional families offer a unique window into the interior composition of asteroid populations. Previous dynamical studies of the Jupiter Trojans have uncovered a handful of potential collisional families, two of which have been subsequently confirmed through spectral characterization. In this paper, we present new multiband photometric observations of the proposed Ennomos family and derive precise g − i colors of 75 candidate family members. While the majority of the targets have visible colors that are indistinguishable from background objects, we identify 13 objects with closely grouped dynamical properties that have significantly bluer colors. We determine that the true Ennomos collisional family is tightly confined to a’_p > 5.29 au and 0.45 < sin i_p < 0.47, and the majority of its confirmed members have near-solar spectral slopes, including some of the bluest objects hitherto discovered in the Trojan population. The property of distinctly neutral colors that is shared by both the Ennomos family and the previously characterized Eurybates family indicates that the spectral properties of freshly exposed surfaces in the Jupiter region are markedly different than the surfaces of uncollided Trojans. This implies that the processes of ice sublimation and space weathering at 5.2 au yield a distinct regolith chemistry from the primordial environment within which the Trojans were initially accreted. It also suggests that the Trojans were emplaced in their present-day location from elsewhere sometime after the initial population formed, which is a key prediction of recent dynamical instability models of solar system evolution.

Item Type:Article
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URLURL TypeDescription
Wong, Ian0000-0001-9665-8429
Brown, Michael E.0000-0002-8255-0545
Additional Information:This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile. Some of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. I.W. is supported by an appointment to the NASA Postdoctoral Program at the NASA Goddard Space Flight Center, administered by Oak Ridge Associated Universities under contract with NASA. We thank Miroslav Brož for detailed comments during the revision process that greatly improved the manuscript.
Group:Division of Geological and Planetary Sciences
Funding AgencyGrant Number
W. M. Keck FoundationUNSPECIFIED
NASA Postdoctoral ProgramUNSPECIFIED
Issue or Number:1
Record Number:CaltechAUTHORS:20230104-583687400.1
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:118661
Deposited By: Research Services Depository
Deposited On:30 Jan 2023 18:14
Last Modified:30 Jan 2023 18:14

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