Cool Stars 14 - Submitted Abstract # 188
This version created on 05 October 2006

Finding ultracool Brown Dwarfs in the CFHTLS


Philippe Delorme, LAOG(Grenoble)
Thierry Forveille, LAOG(Grenoble)
Xavier Delfosse, LAOG(Grenoble)
Chris Willott, HIA(Vancouver)
Loic Albert, CFHT
Annie Robin, LAOB(Besançon)

We present early results of our ongoing search for field Brown Dwarfs
in CFHTLS data.  This survey will identify a very large sample of cool
brown dwarfs, to both find and study the coolest brown dwarfs and
characterize brown dwarfs galactic population.  We extract optimum
photometry from the images, using a new version of Sextractor to
perform dual image PSF-fitting.  We then select Brown Dwarf candidates
on their extreme i'-z' color, and obtain follow-up J-band photometry
to discriminate them from z=6 quasars.  After analysing over 300  sq
deg from CFHTLS Very Wide and Deep image, we have found ~200  new
early L to mid T dwarfs and several late T dwarfs, as well as the
first z>6 quasar outside the SDSS survey.  We obtained spectra of the
most interesting candidates including several very late T dwarfs with
strong methane bands.  The complete survey will have ~1000  L-to mid T
dwarfs, a few dozens late T dwarfs, and hopefully a few Y dwarfs.

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