49 new T dwarfs identified using methane imaging

TL;DR

This paper reports the discovery of 49 new T dwarfs using methane imaging, demonstrating an efficient photometric classification method that can handle large survey data without spectroscopy.

Contribution

The study introduces a new photometric conversion for spectral typing of T4 to T8 brown dwarfs and validates methane differential photometry as an effective classification technique.

Findings

100% confirmation rate of methane-selected brown dwarfs as T dwarfs

Established a new photometric spectral type conversion for T4-T8 dwarfs

Demonstrated methane imaging as an efficient classification method for large surveys

Abstract

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.