Wise/neowise observations of the Hilda population: Preliminary results

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 3 to 200km. We find no size-albedo dependency as reported by other projects. The albedos of our sample are low, with a weighted mean value of p_V = 0.055 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 a weighted mean albedo of p_V = 0.061 0.011, than the general population and dominated by D-type asteroids, while the Schubart collisional family is darker, with a weighted mean albedo of p_V = 0.039 0.013. Using the reflected sunlight in the two shortest WISE bandpasses, we are able to derive a method for taxonomic classification of 10% of the Hildas detected in the NEOWISE survey. For the Hildas with diameter larger than 30km, there are 67⁺⁷ _{- 15}% D-type asteroids and 26⁺¹⁷ _{- 5}% C-/P-type asteroids (with the majority of these being P-types).