Four faint T dwarfs from the UKIRT infrared deep sky survey (UKIDSS) southern stripe

Kuenley Chiu, Michael C. Liu, Linhua Jiang, Katelyn N. Allers, Daniel P. Stark, Andrew Bunker, Xiaohui Fan, Karl Glazebrook, Trent J. Dupuy

Research output: Contribution to journalLetterpeer-review

25 Scopus citations


We present the optical and near-infrared photometry and spectroscopy of four faint T dwarfs newly discovered from the UKIDSS first data release. The sample, drawn from an imaged area of ~136 deg2 to a depth of Y = 19.9 (5σ, Vega), is located in the Sloan Digital Sky Survey (SDSS) Southern Equatorial Stripe, a region of significant future deep imaging potential. We detail the selection and followup of these objects, three of which are spectroscopically confirmed brown dwarfs ranging from type T2.5 to T7.5, and one is photometrically identified as early T. Their magnitudes range from Y = 19.01 to 19.88 with derived distances from 34 to 98 pc, making these among the coldest and faintest brown dwarfs known. The T7.5 dwarf appears to be single based on 0.05-arcsec images from Keck laser guide star adaptive optics. The sample brings the total number of T dwarfs found or confirmed by UKIDSS data in this region to nine, and we discuss the projected numbers of dwarfs in the future survey data. We estimate that ~240 early and late T dwarfs are discoverable in the UKIDSS Large Area Survey (LAS) data, falling significantly short of published model projections and suggesting that initial mass functions and/or birth rates may be at the low end of possible models. Thus, deeper optical data have good potential to exploit the UKIDSS survey depth more fully, but may still find the potential Y dwarf sample to be extremely rare.

Original languageEnglish (US)
Pages (from-to)L53-L57
JournalMonthly Notices of the Royal Astronomical Society: Letters
Issue number1
StatePublished - Mar 2008


  • Catalogues
  • Infrared: stars
  • Stars: low-mass brown dwarfs
  • Surveys
  • Techniques: photometric
  • Techniques: spectroscopic

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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