Eight new T4.5–T7.5 dwarfs discovered in the UKIDSS Large Area Survey Data Release 1
Version 2 2025-01-15, 01:03Version 2 2025-01-15, 01:03
Version 1 2023-05-17, 14:33Version 1 2023-05-17, 14:33
journal contribution
posted on 2025-01-15, 01:03authored byN Lodieu, DJ Pinfield, SK Legget, RF Jameson, DJ Mortlock, SJ Warren, B Burningham, PW Lucas, K Chiu, MC Liu, BP Venemans, RG McMahon, F Allard, I Baraffe, D Barrado y Navacues, G Carraro, SL Casewell, G Chabrier, RJ Chappelle, F Clarke, AC Day-Jones, NR Deacon, PD Dobbie, SL Folkes, NC Hambly, PC Hewett, ST Hodgkin, HRA Jones, TR Kendall, A Magazzu, EL Martin, MJ McCaughrean, T Nakajima, Y Pavlenko, M Tamura, CG Tinney, MR Zapatero Osorio
We present eight new T4.5–T7.5 dwarfs identified in the UKIRT (United Kingdom Infrared Telescope) Infrared Deep Sky Survey (UKIDSS) Large Area Survey (LAS) Data Release 1 (DR1). In addition we have recovered the T4.5 dwarf SDSS J020742.91+000056.2 and the T8.5 dwarf ULAS J003402.77−005206.7. Photometric candidates were picked up in two-colour diagrams over 190 deg2 (DR1) and selected in at least two filters. All candidates exhibit near-infrared spectra with strong methane and water absorption bands characteristic of T dwarfs and the derived spectral types follow the unified scheme of Burgasser et al.. We have found six new T4.5–T5.5 dwarfs, one T7 dwarf, one T7.5 dwarf and recovered a T4.5 dwarf and a T8.5 dwarf. We provide distance estimates which lie in the 15–85 pc range; the T7.5 and T8.5 dwarfs are probably within 25 pc of the Sun. We conclude with a discussion of the number of T dwarfs expected after completion of the LAS, comparing these initial results to theoretical simulations.