Toward a Taxonomy of the Edgeworth–Kuiper Objects: A Multivariate Approach

The principal component (PC) and G-mode multivariate statisticshave been used in analysing the set of the 34 Edgeworth–Kuiper objects (EKOs) – 23 Trans NeptunianObjects (TNO) and 11 Centaurs – for which B, V, R, I, J homogeneous photometry were available.The results obtained show that V-I and V-Js are the key parameters in structuring the sample inhomogeneous groups. The PC1 axis (which contains ∼93% of the sample total variance) spans fivetimes more than the PC2 (which contains ∼6% of the sample total variance). The extremesof the PC1 axis contain the objects having a flat spectrum (low PC1 values) and a very red spectrumrespectively. Independently, the G-mode analysis allows us to distinguish six homogeneous groups of objectswhich confirm and extend the results obtained with the PC analysis. In addition to these groups, a few objectsremain not included in any group (i.e., does not have significant similitude with other objects) and yet givean indication of a more complex compositional structure of the sample. These preliminary results will haveto be confirmed and completed when a larger sample is available, but they provide some interesting hintsfor understanding the – mainly collisional – evolution of the EKOs.