the actual transmission and detector sensitivity of the MegaCam and WIRCam instruments used in CFBDSIR. \[wilkins\]](14277fg4.ps)

Results
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Photometric confirmation of 3 ultracool brown dwarfs
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The 55 candidates found in a 66 square degree subset of the data were followed-up with photometry at the ESO New Technology Telescope, using the SOFI near infrared camera during visitor mode runs 083.C-0797(A) and 082.C-0506(A), in July 2009 and March 2009. These pointed NIR observations confirm six T-dwarfs, of which 3 are robust ultracool brown dwarf candidates. Those are likely to be either very late T-dwarfs ($>$T8) or cooler Y dwarfs. The brighter 2 of the 3 earlier T candidates are re-identifications of CFBDS-discovered brown dwarfs, spectroscopically confirmed as T3.5 and T5 (Albert et al., submitted.).

The candidates identified in the remaining 269 square degrees have not yet been followed-up, and they certainly include mostly contaminants. Extrapolating the results from the 66 square degree pilot subset of CFBDSIR to the full survey, we expect to find $\sim$15 ultracool brown dwarfs. Low-resolution NIR spectroscopy of the confirmed ultracool brown dwarfs will be needed to derive spectral types and characterise their cool atmosphere physics.\
[**Photometric properties of ultra-red brown dwarf candidates**]{}

![Colour-colour diagram of some 