49 new T dwarfs identified using methane imaging

Cardoso, C. V., Burningham, B., Smart, R. L., Spaandonk, L. van, Baker, D., Smith, L. C., Andrei, A.H., Bucciarelli, B., Dhital, S., Jones, H.R.A., Lattanzi, M. G., Magazzu, A., Pinfield, D.J. and Tinney, C. G. (2015) 49 new T dwarfs identified using methane imaging. Monthly Notices of the Royal Astronomical Society (MNRAS), 450 (3). pp. 2486-2499. ISSN 0035-8711

Copy

We present the discovery of 49 new photometrically classified T dwarfs from the combination of large infrared and optical surveys combined with follow-up TNG photometry. We used multi-band infrared and optical photometry from the UKIRT 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 CH4s - CH4l colour and spectral type for T4 to 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% 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.