Extending the Canada-France Brown Dwarf Survey to the near infrared

¹ School of Physics & Astronomy, University of St Andrews North Haugh, St Andrews KY16 9SS, Scotland
² Canada-France-Hawaii Telescope Corporation, 65-1238 Mamalahoa Highway, Kamuela, HI96743, USA
³ Département de physique and Observatoire du Mont Mégantic, Université de Montréal, CP. 6128, Succursale Centre-Ville, Montréal, QC H3C 3J7, Canada
⁴ Laboratoire d’Astrophysique de Grenoble, UMR5571 (CNRS and Université J. Fourier), BP. 53, 38041 Grenoble Cedex 9, France
⁵ Observatoire de Besançon, Institut Utinam, UMR CNRS 6213, BP. 1615, 25010 Besançon Cedex, France
⁶ University of Ottawa, Physics Department, 150 Louis Pasteur, MacDonald Hall, Ottawa, ON K1N 6N5, Canada
⁷ Institut d’Astrophysique de Paris-CNRS, 98bis Boulevard Arago, 75014 Paris, France
⁸ C.R.A.L. (UMR 5574 CNRS), École Normale Supérieure, 69364 Lyon Cedex 07, France
⁹ Gemini Observatory Southern Operations Center c/o AURA, Casilla 603 La Serena, Chile

^a e-mail: pd10@st-andrews.ac.uk

Abstract

We present the first results of the Canada-France Brown Dwarfs Survey-InfraRed, hereafter CFBDSIR, our near infrared extension to the optical wide field survey CFBDS. Our final objectives are to constrain ultracool atmosphere physics by finding a statistically significant sample of objects cooler than 600K and to explore the ultracool brown dwarf mass function building on a well defined sample of such objects. We identify candidates in CFHT/Wircam J and CFHT/MegaCam z′ images using optimized psf-fitting within Source Extractor, and follow them up with pointed near infrared imaging with SOFI at NTT. We have so far analysed and followed up all candidates on the first 66 square degrees of the 280 square degrees survey. We identified 64 T dwarfs candidates with z′− J > 3.5 and have confirmed 3 of them as ultracool brown dwarfs (later than T7 dwarfs and Y dwarfs candidates), and 14 of them as early and mid-T dwarfs based on their far red and NIR colours. We also present here the NIR spectra of one of these ultracool dwarfs, CFBDSIR1458 which confirms it as one of the coldest brown dwarf known, in the 500–600 K temperature range.