A new brown dwarf desert? A scarcity of wide ultracool binaries

We present the results of a deep-imaging search for wide companions to low-mass stars and brown dwarfs using NSFCam on the Infrared Telescope Facility. We searched a sample of 132 M7-L8 dwarfs to magnitude limits of J similar to 20.5 and K similar to 18.5, corresponding to secondary-to-primary mass ratios of similar to 0.5. No companions were found with separations between 2" and 31" (similar to 40 to similar to 1000 AU). This null result implies a wide companion frequency below 2.3% at the 95% confidence level within the sensitivity limits of the survey. Preliminary modeling efforts indicate that we could have detected 85% of companions more massive than 0.05 M-circle dot and 50% above 0.03 M-circle dot.