around them, permitting the study of ultracool dwarfs not only as individual interesting objects, but as a population. This will help define the T/Y spectral transition that is expected to occur in this temperature range. In section 1 we present the rationale of this new wide-field survey and the observations at its core. In section 2 we describe the data reduction and the data analysis methods we used to identify ultracool brown dwarfs candidates. Finally, we present the spectra and the photometry of the first ultracool brown dwarf identified with CFBDSIR in section 3.

Observations
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Far-red and near infrared photometric properties of brown dwarfs
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Field brown dwarfs are cool objects, with a temperature range that currently extends from $\sim$2500K (early L) to $\sim 525$K [latest objects identified, e.g. @Leggett.2009]. Even cooler, and still to be found, brown dwarfs should close the temperature gap between late type T-dwarfs and solar system Jovian planets($\sim$110K). These objects do exist [see @Burgasser.2009proc for instance] because low-mass brown dwarfs already observed in young clusters must cool down to this temperature range when they age. Brown dwarfs spectra differ significantly from a black body, and have considerable structure from deep absorption lines and bands. 