Taxonomic classification of asteroids based on MOVIS near-infrared colors

Abstract

We aim to provide a taxonomic classification for asteroids observed by VISTA-VHS survey. We derive a method for assigning a compositional type to an object based on its (Y-J), (J-Ks), and (H-Ks) colors. We present a taxonomic classification for 18\,265 asteroids from the MOVIS catalog, using a probabilistic method and the k-nearest neighbors algorithm. Because our taxonomy is based only on NIR colors, several classes from Bus-DeMeo were clustered into groups and a slightly different notation was used (i.e. the superscript indicates that the classification was obtained based on the NIR colors and the subscript indicates possible miss-identifications with other types). Our results are compared with the information provided by the Sloan Digital Sky Survey (SDSS) and Wide-field Infrared Survey Explorer (WISE). The two algorithms used in this study give a taxonomic type for all objects having at least (Y-J) and (J-Ks) observed colors. A final classification is reported for a set of 6\,496 asteroids based on the criteria that KNN and probabilistic algorithms gave the same result, (Y-J)$_{err}\leq$ 0.118 and (J-Ks)$_{err}\leq$0.136. This set includes 144 bodies classified as $B_k^{ni}$, 613 as $C^{ni}$, 197 as $C_{gx}^{ni}$, 91 as $X_t^{ni}$, 440 as $D_s^{ni}$, 665 as $K_l^{ni}$, 233 as $A_d^{ni}$, 3\,315 as $S^{ni}$, and 798 as $V^{ni}$. We report the albedo distribution for each taxonomic group and we compute new median values for the main types. We found that V-type and A-type candidates have identical size frequency distributions, but the V-types are five times more common than the A-types. Several particular cases, such as the A-type asteroid (11616) 1996 BQ2 and the S-type (3675) Kematsch, both in the Cybele population, are discussed. Files and codes available at: https://github.com/marcelpopescu/MOVIS-Taxonomy