A Volume-Limited Search for L/T Transition Brown Dwarfs With the Pan-STARRS and WISE Surveys

We are conducting a productive wide-field (30,000 deg₂) search for brown dwarfs in the L/T transition (spectral types ≈ L6-T5) within 25 pc using the Pan-STARRS1 (PS1) 3π and WISE all-sky surveys. Previous large-scale searches have been incomplete for L/T transition dwarfs because these objects are faint in optical bands and have near-infrared colors that are difficult to distinguish from background stars. To overcome these obstacles, we have cross-matched the PS1 (optical) and WISE (mid-IR) catalogs to produce a unique multi-wavelength database for finding ultracool dwarfs. We have so far discovered over 80 new L/T transition dwarfs in 3/4 of our search area, 28 of which lie within 25 pc. We have also made several serendipitous discoveries of field L dwarfs showing extreme cloud-induced reddening and/or spectroscopic signatures of youth. We are identifying a well-defined, volume-limited sample of dozens of late L and early T dwarfs, which will be used to better understand and model the evolution of brown dwarfs through the L/T transition.