Program: GN-2007B-Q-3

The CFHT Legacy Survey (CFHTLS) is progressing very well and continues to deliver a goldmine of information. To date, over 370 square degrees have been analyzed to isolate very red brown dwarf candidates, most of which are probably T dwarfs or dwarfs at the L-T transition. Among those, a handfull are exceptionally red objects with i-z>3.0, redder than the coldest T dwarf known (~750 K), and could well be the first candidates of a new class of BDs - the Y dwarfs - expected to harbor ammonia absorption bands. We propose to obtain cross-dispersed spectra with GNIRS and H-band NIRI spectra for the Northern candidates on ~20 targets (J_vega=17.5 to J_vega=18.5) in TOO time to assess their temperature and look for ammonia spectral features. This is the third proposal we submit for this project. Of the four candidates observed in semester 2006A, 3 are BDs of spectral types T1, T4 and T5 while one is a quasar at z=6, of which only ~10 were previously known. Observations are ongoing on 12 more candidates (GS-2007A-Q-1). This proposal requests 12 hours on Gemini South, an accompanying proposal requests 7 hours on Gemini North.