Four Faint T Dwarfs from the UKIRT Infrared Deep Sky Survey (UKIDSS) Southern Stripe

Abstract

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 square degrees to a depth of Y=19.9 (5-sigma, Vega), is located in the 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 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 LAS data, falling significantly short of published model projections and suggesting that IMFs and/or birthrates may be at the low end of possible models. Thus, deeper optical data has good potential to exploit the UKIDSS survey depth more fully, but may still find the potential Y dwarf sample to be extremely rare.

arXiv commentAccepted for publication in MNRAS Letters

References in corpus (26)

• The UKIRT Infrared Deep Sky Survey (UKIDSS)
• Evolutionary models for cool brown dwarfs and extrasolar giant planets. The case of HD 20945
• The Second Data Release of the Sloan Digital Sky Survey
• A Method of Correcting Near-Infrared Spectra for Telluric Absorption
• The UKIRT Infrared Deep Sky Survey ZYJHK Photometric System: Passbands and Synthetic Colours
• Near-Infrared Photometry and Spectroscopy of L and T Dwarfs: the Effects of Temperature, Clouds, and Gravity
• A Unified Near Infrared Spectral Classification Scheme for T Dwarfs
• The WFCAM Science Archive
• Towards Spectral Classification of L and T Dwarfs: Infrared and Optical Spectroscopy and Analysis
• A Modified Magnitude System that Produces Well-Behaved Magnitudes, Colors, and Errors Even for Low Signal-to-Noise Ratio Measurements
• The Spectra of T Dwarfs I: Near-Infrared Data and Spectral Classification
• Seventy-One New L and T Dwarfs from the Sloan Digital Sky Survey
• Hubble Space Telescope NICMOS Observations of T Dwarfs: Brown Dwarf Multiplicity and New Probes of the L/T Transition
• The UKIRT Infrared Deep Sky Survey First Data Release
• The Discovery of a Field Methane Dwarf from Sloan Digital Sky Survey Commissioning Data
• SDSS J1534+1615AB: A Novel T Dwarf Binary Found with Keck Laser Guide Star Adaptive Optics and the Potential Role of Binarity in the L/T Transition
• A very cool brown dwarf in UKIDSS DR1
• Physical and Spectral Characteristics of the T8 and Later-Type Dwarfs
• Eight new T4.5-T7.5 dwarfs discovered in the UKIDSS Large Area Survey Data Release 1
• The discovery of the first luminous z~6 quasar in the UKIDSS Large Area Survey
• A Spectroscopic Survey of Faint Quasars in the SDSS Deep Stripe: I. Preliminary Results from the Co-added Catalog
• Mid-Infrared Selection of Brown Dwarfs and High-Redshift Quasars
• Two T dwarfs from the UKIDSS Early Data Release
• The Optical and Near-Infrared Properties of 2837 Quasars in the UKIRT Infrared Deep Sky Survey (UKIDSS)
• The possiblity of detection of Ultracool Dwarfs with the UKIRT Infrared Deep Sky Survey
• The Color Selection of Quasars from Redshifts 5 to 10: Cloning and Discovery

Cited by in corpus (12)

• Photometry and Proper Motions of M, L, and T Dwarfs from the Pan-STARRS1 3$\pi$ Survey
• Seventy six T dwarfs from the UKIDSS LAS: benchmarks, kinematics and an updated space density
• Forty seven new T dwarfs from the UKIDSS Large Area Survey
• Brown dwarfs and very low mass stars in the Hyades cluster : a dynamically evolved mass function
• Fifteen new T dwarfs discovered in the UKIDSS Large Area Survey
• A new benchmark T8-9 brown dwarf and a couple of new mid-T dwarfs from the UKIDSS DR5+ LAS
• NPARSEC: NTT Parallaxes of Southern Extremely Cool objects. Goals, targets, procedures and first results
• The distance to the cool T9 brown dwarf ULAS J003402.77-005206.7
• Extremely faint high proper motion objects from SDSS stripe 82 - Optical classification spectroscopy of about 40 new objects
• The SRG/eROSITA All-Sky Survey: X-ray beacons at late cosmic dawn
• Two distant brown dwarfs in the UKIRT Infrared Deep Sky Survey Deep Extragalactic Survey Data Release 2
• Probing Late-type T dwarf J-H Color Outliers for Signs of Age