Bibcode
Lodieu, N.; Burningham, B.; Hambly, N. C.; Pinfield, D. J.
Bibliographical reference
Monthly Notices of the Royal Astronomical Society, Volume 397, Issue 1, pp. 258-264.
Advertised on:
7
2009
Citations
17
Refereed citations
14
Description
We present the discovery of two new late-T dwarfs identified in the
UKIRT Infrared Deep Sky Survey (UKIDSS) Galactic Clusters Survey (GCS)
Data Release 2 (DR2). These T dwarfs are nearby old T dwarfs along the
line of sight to star-forming regions and open clusters targeted by the
UKIDSS GCS. They are found towards the αPer cluster and Orion
complex, respectively, from a search in 54deg2 surveyed in
five filters. Photometric candidates were picked up in two-colour
diagrams, in a very similar manner to candidates extracted from the
UKIDSS Large Area Survey (LAS) but taking advantage of the Z filter
employed by the GCS. Both candidates exhibit near-infrared J-band
spectra with strong methane and water absorption bands characteristic of
late-T dwarfs. We derive spectral types of T6.5 +/- 0.5 and T7 +/- 1 and
estimate photometric distances less than 50 pc for UGCS
J030013.86+490142.5 and UGCS J053022.52-052447.4, respectively. The
space density of T dwarfs found in the GCS seems consistent with
discoveries in the larger areal coverage of the UKIDSS LAS, indicating
one T dwarf in 6-11deg2. The final area surveyed by the GCS,
1000deg2 in five passbands, will allow expansion of the LAS
search area by 25 per cent, increase the probability of finding
ultracool brown dwarfs, and provide optimal estimates of contamination
by old field brown dwarfs in deep surveys to identify such objects in
open clusters and star-forming regions.
Based on observations made with the United Kingdom Infrared Telescope,
operated by the Joint Astronomy Centre on behalf of the U.K. Science
Technology and Facility Council.
E-mail: nlodieu [at] iac.es (nlodieu[at]iac[dot]es)