Program: GN-2008A-Q-15

Y-dwarfs are the as yet undiscovered spectral class, cooler even than the known T dwarfs. Expected within the Teff~700-400K range, Y spectral characteristics may show evidence of atmospheric water clouds and strong ammonia absorption, and their discovery is a key science driver for the UKIDSS Large Area Survey (LAS). This proposal requests 47.9hrs to continue our triggering program with NIRI to spectroscopically confirm the first Y-dwarfs from amongst the very late T-like objects identified in the LAS. Our program has recently confirmed the first T8.5 dwarf ever, with a Teff~650-700K, using the first two UKIDSS data releases (Dr1 and Dr2). In 08A we will search a much larger area of sky (~1000 sq degs), and should discover ~60 late T dwarfs, ~15 of the rare T7.5+ objects, and ~3-5 potential record breakers with Teff=600-750K. Our 08A program has the greatest potential yet for discovering the prototype Y-dwarf.