Cardoso, C. V.C. V.CardosoBurningham, B.B.BurninghamSMART, Richard LaurenceRichard LaurenceSMART0000-0002-4424-4766van Spaandonk, L.L.van SpaandonkBaker, D.D.BakerSmith, L. C.L. C.SmithZhang, Z. H.Z. H.ZhangAndrei, A. H.A. H.AndreiBUCCIARELLI, BeatriceBeatriceBUCCIARELLI0000-0002-5303-0268Dhital, S.S.DhitalJones, H. R. A.H. R. A.JonesLATTANZI, Mario GilbertoMario GilbertoLATTANZI0000-0003-0429-7748MAGAZZU', AntonioAntonioMAGAZZU'0000-0003-1259-4371Pinfield, D. J.D. J.PinfieldTinney, C. G.C. G.Tinney2020-03-142020-03-1420150035-8711http://hdl.handle.net/20.500.12386/23241The author's would like to thank the staff of the TNG for their excellent support during of the very large programme on which this work is based. BB acknowledges financial support from the European Commission in the form of a Marie Curie International Outgoing Fellowship (PIOF-GA-2013-629435). This research has benefitted from the SpeX Prism Spectral Libraries, maintained by Adam Burgasser at http://pono.ucsd.edu/∼adam/browndwarfs/spexprism . The authors also acknowledge the Marie Curie 7th European Community Framework Programme grant no. 236735 Parallaxes of Southern Extremely Cool objects (PARSEC) International Incoming Fellowship and grant no. 247593 Interpretation and Parametrization of Extremely Red COOL dwarfs (IPERCOOL) International Research Staff Exchange Scheme. Based on observations made with the Italian TNG operated on the island of La Palma by the Fundacin Galileo Galilei of the Istituto Nazionale di Astrofisica at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias. The United Kingdom Infrared Telescope (UKIRT) was operated by the Joint Astronomy Centre on behalf of the Science and Technology Facilities Council of the UK. This work is based in part on data obtained as part of the UKIRT Infrared Deep Sky Survey.We present the discovery of 49 new photometrically classified T dwarfs from the combination of large infrared and optical surveys combined with follow-up Telescopio Nazionale Galileo photometry. We used multiband infrared and optical photometry from the United Kingdom Infrared Telescope and Sloan Digital Sky Surveys to identify possible brown dwarf candidates, which were then confirmed using methane filter photometry. We have defined a new photometric conversion between CH<SUB>4</SUB>s - CH<SUB>4</SUB>l colour and spectral type for T4-T8 brown dwarfs based on a part of the sample that has been followed up using methane photometry and spectroscopy. Using methane differential photometry as a proxy for spectral type for T dwarfs has proved to be a very efficient technique. Of a subset of 45 methane selected brown dwarfs that were observed spectroscopically, 100 per cent were confirmed as T dwarfs. Future deep imaging surveys will produce large samples of faint brown dwarf candidates, for which spectroscopy will not be feasible. When broad wavelength coverage is unavailable, methane imaging offers a means to efficiently classify candidates from such surveys using just a pair of near-infrared images.STAMPAenArticle10.1093/mnras/stv3802-s2.0-84930827541000356339300021https://academic.oup.com/mnras/article/450/3/2486/1054563http://arxiv.org/abs/1502.06503v12015MNRAS.450.2486CFIS/05 - ASTRONOMIA E ASTROFISICA