Taxonomy of trans-Neptunian objects and Centaurs as seen from spectroscopy

Abstract

Context. Taxonomy of trans-Neptunian objects (TNOs) and Centaurs has been made in previous works using broadband filters in the visible and near infrared ranges. This initial investigation led to the establishment of four groups with the aim to provide the mean colors of the different classes with possible links with any physical or chemical properties. However, this taxonomy was only made with the Johnson-Cousins filter system and the ESO J, H, Ks filters combination, and any association with other filter system is not yet available. Aims. We aim to edit complete visible to near infrared taxonomy and extend this work to any possible filters system. To do this, we generate mean spectra for each individual group, from a data set of 43 spectra. This work also presents new spectra of the TNO (38628) Huya, on which aqueous alteration has been suspected, and the Centaur 2007 VH305. Methods. To generate the mean spectra for each taxonomical group, we first averaged the data for each of the four taxonomical groups and checked that spectroscopic and photometric data were consistent according to their relative errors. Results. We obtained four complete spectra corresponding to the different classes from 0.45 to 2.40 microns. Our results based on spectroscopy are in good agreements with those obtained in photometry for the bluest (BB) and reddest (RR) objects. At the contrary, no clear patterns appear for the two intermediate groups (BR and IR). Both BR and IR mean-spectra are almost intermixed, probably due to the fact that part of these objects have not always clear affiliation to one particular taxonomical group. Conclusions. We provide mean spectra that could be used to edit colors in different filters system working in this wavelength range. This work clearly establish the mean spectra of the BB and RR group while the two other groups need probably further refinement.