Program: GN-2013A-Q-20

We propose to continue our highly-successful survey of rare substellar objects selected from Pan-STARRS 1. We will continue to mine the sample of objects selected on the basis of PS1-to-PS1 proper motions. Until recently, the work has relied on PS1+2MASS to determine the proper motion and has been limited in depth by 2MASS. The PS1-only proper motions are now an option for most of the sky, as we have sufficient baseline in most areas of the 3pi Survey. PS1+PS1 proper motions are a unique resource and allow to select a larger sample of interesing candidates, to study the Galactic Plane, and to go after objects most likely to be the interesting exotica: late T-dwarfs, L and T dwarfs with extreme or anomalous colors. In most previous semesters, we have been using PS1 and 2MASS observations to select brown dwarf candidates based on proper motion and colors. We have used UKIRT photometry to extract the high-probability substellar candidates for follow-up spectroscopy at IRTF. This process has been extremely efficient, with nearly 100% spectroscopy success for the objects in our high priority sample. The PS1+2MASS sample is now essentially exhausted, and we are now working on the PS1-PS1 sample to extend the depth of the survey. This new sample is more pristine before we go to UKIRT, but still requires JHK photometry for spectroscopy prioritization. Our use of UKIRT for this program is critical because of the fast turn around of the data. We have been working with the data processing group at the Cambridge Astronomy Survey Unit to retrieve the processed images quickly, allowing us to obtain IRTF spectroscopy of the filtered candidates within 10 days of the UKIRT observations. This fast turn-around, currently not available from CFHT, is critical not only for feeding the follow-up IRTF observations, but also to keep us ahead of our competition. Without the fast turn around, we will lose nearly a year in the follow-up, putting us at a severe disadvantage. The closure of UKIRT following UH2013A makes this the last semester in which we can employ this successful strategy. The discovery of these rare substellar objects is critical to sample under-explored portions of parameter space. Our program takes advantage of the large area, depth, and proper-motion accuracy of the PS1 3π data to search for the rarest members of the nearby solar neighborhood: the coolest of the T-dwarfs and ultracool subdwarfs. Our program also allows us to find objects with anomalous colors for their spectral class. These may be caused by young age or low metallicity, or they may be caused by specific atmospheric conditions (eg large grains or clouds). A large sample of such anomalous objects allows us to make statistical statements about these effects. We are also proposing follow-up spectroscopy of 10 of these exotic low-mass objects discovered to date.