Col-OSSOS: z Band Photometry Reveals Three Distinct TNO Surface Types
Résumé
The surface reflectance of trans-Neptunian object (TNO) surfaces in g, r, and z band provides a tool for separating TNOs into three surface classifications: dynamically excited red surfaces, dynamically excited neutral surfaces, and red cold classical surfaces. Photometry of 26 TNOs obtained at Gemini and Subaru Telescopes as part of the Colours of the Outer Solar System Survey (Col-OSSOS) demonstrates that the inclusion of z band uniquely identifies cold classical surfaces. The dynamically excited objects using this surface color combination are consistent with two surface classes based on the two-component mixing models of Fraser & Brown (2012). The reflectance of the neutral component of the models in g, r, and z band is consistent with the speculation from that work that the neutral material contains silicates. Photometry in these three wavelenghts provides a powerful tool for identifying TNO surface types, and in particular objects with cold classical-like surfaces. This tool enables the identification of dynamically hot interlopers in the cold classical population and primordially cold classical objects in dynamically excited orbits.