Kendall, TR and Tamura, M and Tinney, CG and Martin, EL and Ishii, M and Pinfield, DJ and Lucas, PW and Jones, HRA and Leggett, SK and Dye, S and Hewett, PC and Allard, F and Baraffe, I and Barrado y Navascues, D and Carraro, G and Casewell, SL and Chabrier, G and Chappelle, RJ and Clarke, F and Day-Jones, A and Deacon, N and Dobbie, PD and Folkes, S and Hambly, NC and Hodgkin, ST and Nakajima, T and Jameson, RF and Lodieu, N and Magazzu, A and McCaughrean, MJ and Pavlenko, YV and Tadashi, N and Zapatero Osorio, MR, Two T dwarfs from the UKIDSS early data release, Astronomy and Astrophysics: A European Journal, 466, (3) pp. 1059 - 1064. ISSN 0004-6361 (2007) [Refereed Article]
Copyright 2007 ESO
Context: We report on the first ultracool dwarf discoveries from the UKIRT Infrared Deep Sky Survey (UKIDSS) Large Area Survey Early Data Release (LAS EDR), in particular the discovery of T dwarfs which are fainter and more distant than those found using the 2MASS and SDSS surveys.
Aims: We aim to show that our methodologies for searching the ~27 deg2 of the LAS EDR are successful for finding both L and T dwarfs via cross-correlation with the Sloan Digital Sky Survey (SDSS) DR4 release. While the area searched so far is small, the numbers of objects found shows great promise for near-future releases of the LAS and great potential for finding large numbers of such dwarfs.
Methods: Ultracool dwarfs are selected by combinations of their YJH(K)$ UKIDSS colours and SDSS DR4 z - J and i - z colours, or, lower limits on these red optical/infrared colours in the case of DR4 dropouts. After passing visual inspection tests, candidates have been followed up by methane imaging and spectroscopy at 4 m and 8 m-class facilities.
Results: Our main result is the discovery following CH4 imaging and spectroscopy of a T4.5 dwarf, ULAS J 1452+0655, lying ~80 pc distant. A further T dwarf candidate, ULAS J 1301+0023, has very similar CH4 colours but has not yet been confirmed spectroscopically. We also report on the identification of a brighter L0 dwarf, and on the selection of a list of LAS objects designed to probe for T-like dwarfs to the survey J-band limit.Conclusions: Our findings indicate that the combination of the UKIDSS LAS and SDSS surveys provide an excellent tool for identifying L and T dwarfs down to much fainter limits than previously possible. Our discovery of one confirmed and one probable T dwarf in the EDR is consistent with expectations from the previously measured T dwarf density on the sky.
|Item Type:||Refereed Article|
|Keywords:||infrared: stars -- stars: low-mass, brown dwarfs -- stars: fundamental parameters|
|Research Division:||Physical Sciences|
|Research Group:||Astronomical and Space Sciences|
|Research Field:||Stellar Astronomy and Planetary Systems|
|Objective Division:||Expanding Knowledge|
|Objective Group:||Expanding Knowledge|
|Objective Field:||Expanding Knowledge in the Physical Sciences|
|UTAS Author:||Dobbie, PD (Dr Paul Dobbie)|
|Web of Science® Times Cited:||32|
|Deposited By:||Mathematics and Physics|
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