Searching for primitive, dark, spectrally red asteroid families in the main belt with Gaia

TL;DR

This study uses Gaia DR3 spectra to identify and reclassify certain dark asteroid families in the main belt as potentially primitive, hydrated, and organic-rich T-/D-types, highlighting their possible contribution to near-Earth asteroid populations.

Contribution

It introduces a spectral analysis approach to reclassify asteroid families, revealing their true spectral types and potential primitive compositions.

Findings

Eight asteroid families are reclassified as T-/D-type based on spectral slopes.

Some families may contribute to near-Earth asteroid populations.

Further near-infrared observations are needed for confirmation.

Abstract

Dark asteroids with featureless neutral to red spectra are of particular interest due to their ability to potentially harbour primitive, hydrated, and possibly organic-rich material. These asteroids belong to the spectroscopic C-complex, to the X-types with low geometric visible albedo values as well as to the T- and D-type end members of the Bus-DeMeo spectroscopic taxonomy. Here we used Gaia Data Release 3 visible reflectance spectra to study the average spectral profiles of the C- and X-complex asteroid families in the central and outer main belt (orbital semi-major axis between 2.5 - 3.7~au). We found that eight of these families, namely 96 Aegle, 627 Charis, 1484 Postrema and 5438 Lorre, previously classified as C-complex families, and 322 Phaeo, 1303 Luthera, 5567 Durisen and 53546 2000BY6 previously classified as X-complex families, have redder slopes than implied by their previous classification and could be better classified as T-/D-type families. Some of these families may also feed the near-Earth asteroid population, being responsible for the observed T-/D-type excess. However, the analysis of their principal components of Gaia Data Release 3 spectra suggest that further near-infrared observations are needed in order to verify this identification.