Spectroscopic study of Ceres’ collisional family candidates

Abstract

Context. Despite the observed signs of large impacts on the surface of Ceres, there is no confirmed collisional family associated with this dwarf planet. After a dynamical and photometric study, a sample of 156 asteroids were proposed as candidate members of a Ceres collisional family. Aims. Our main objective is to study the connection between Ceres and a total of 14 observed asteroids among the candidates sample to explore their genetic relationships with Ceres. Methods. We obtained visible spectra of these 14 asteroids using the OSIRIS spectrograph at the 10.4 m Gran Telescopio Canarias. We computed spectral slopes in two different wavelength ranges, from 0.49 to 0.80 μm and from 0.80 to 0.92 μm, to compare the values obtained with those on Ceres’ surface previously computed using the Visible and Infrared Spectrometer instrument on board the NASA Dawn spacecraft. We also calculated the spectral slopes in the same range for ground-based observations of Ceres collected from the literature. Results. We present the visible spectra and the taxonomy of 14 observed asteroids. We found that only two of the asteroids are spectrally compatible with Ceres’ surface. Further analysis of those two asteroids indicates that they are spectrally young and thus less likely to be members of the Ceres family. Conclusions. All in all, our results indicate that most of the 14 observed asteroids are not likely to belong to a Ceres collisional family. Despite two of them being spectrally compatible with the young surface of Ceres, further evaluation is needed to confirm or reject their origin from Ceres.