Program: GS-2006B-Q-36

Y dwarfs are the as yet undiscovered Teff~700-400K sub-stellar objects cooler even than the known methane or T dwarfs (Teff~1300-700K). Y spectral characteristics may show evidence of atmospheric water clouds and strong ammonia absorption, and their discovery is a key science driver for the UKIRT Infrared Deep Sky Survey (UKIDSS). This proposal requests 8.03 hrs of quick response Gemini South time to use GNIRS to followup the best Y dwarf candidates found in UKIDSS data, and thus attempt to discover the first Y dwarf as early as possible. Such a find would be a high profile discovery for both UKIDSS and Gemini, but more importantly, knowledge of actual Y dwarf colours (and the T-Y colour trend) will allow us to optimally mine UKIDSS, facilitating efficient discovery of larger Y dwarf samples, and a rapid turn around in our exploitation of LAS Y dwarf science.