WISE/NEOWISE Observations of the Hilda Population: Preliminary Results

Abstract

We present the preliminary analysis of 1023 known asteroids in the Hilda region of the Solar System observed by the NEOWISE component of the Wide-field Infrared Survey Explorer (WISE). The sizes of the Hildas observed range from $\sim 3-200$km. We find no size - albedo dependency as reported by other projects. The albedos of our sample are low, with a weighted mean value $p_V=0.055\pm 0.018$, for all sizes sampled by the NEOWISE survey. We observed a significant fraction of the objects in the two known collisional families in the Hilda population. It is found that the Hilda collisional family is brighter, with weighted mean albedo of $p_V=0.061\pm 0.011$, than the general population and dominated by D-type asteroids, while the Schubart collisional family is darker, with weighted mean albedo of ($p_V=0.039\pm 0.013$). Using the reflected sunlight in the two shortest WISE bandpasses we are able to derive a method for taxonomic classification of $\sim 10$ of the Hildas detected in the NEOWISE survey. For the Hildas with diameter larger than 30km there are $67_{-15}^{+7}$ D-type asteroids and $26_{-5}^{+17}$ C-/P-type asteroids (with the majority of these being P-types).

Accepted for publication in Astrophysical Journal. Electronic table to be published on the publishers website