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arXiv · 0804.1477

Finding ultracool brown dwarfs with MegaCam on CFHT: method and first results

Philippe Delorme·Chris J. Willott·Thierry Forveille·Xavier Delfosse·Céline Reylé·Emmanuel Bertin·Loic Albert·Etienne Artigau·Annie C. Robin·France Allard·Rene Doyon·Gary J. Hill
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Abstract

We present the first results of a wide field survey for cool brown dwarfs with the MegaCam camera on the CFHT telescope, the Canada-France Brown Dwarf Survey, hereafter CFBDS. Our objectives are to find ultracool brown dwarfs and to constrain the field-brown dwarf mass function thanks to a larger sample of L and T dwarfs. We identify candidates in CFHT/MegaCam i' and z' images using optimised psf-fitting within Source Extractor, and follow them up with pointed near-infrared imaging on several telescopes. We have so far analysed over 350 square degrees and found 770 brown dwarf candidates brighter than z'{AB}=22.5. We currently have J-band photometry for 220 of these candidates, which confirms 37% as potential L or T dwarfs. Some are among the reddest and farthest brown dwarfs currently known, including an independent identification of the recently published ULAS J003402.77-005206.7 and the discovery of a second brown dwarf later than T8, CFBDS J005910.83-011401.3. Infrared spectra of three T dwarf candidates confirm their nature, and validate the selection process. The completed survey will discover ~100 T dwarfs and ~500 L dwarfs or M dwarfs later than M8, approximately doubling the number of currently known brown dwarfs. The resulting sample will have a very well-defined selection function, and will therefore produce a very clean luminosity function.

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Philippe Delorme, Chris J. Willott, Thierry Forveille, Xavier Delfosse, Céline Reylé, Emmanuel Bertin, Loic Albert, Etienne Artigau, Annie C. Robin, France Allard, Rene Doyon, Gary J. Hill. 2008-04-09. Finding ultracool brown dwarfs with MegaCam on CFHT: method and first results. https://doi.org/10.1051/0004-6361:20078843

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