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New Y and T Dwarfs from WISE Identified by Methane Imaging

Tinney, C. J. and Kirkpatrick, J. Davy and Faherty, Jacqueline K. and Mace, Gregory N. and Cushing, Mike and Gelino, Christopher R. and Burgasser, Adam J. and Sheppard, Scott S. and Wright, Edward L. (2018) New Y and T Dwarfs from WISE Identified by Methane Imaging. Astrophysical Journal Supplement Series, 236 (2). Art. No. 28. ISSN 0067-0049. doi:10.3847/1538-4365/aabad3.

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We identify new Y- and T-type brown dwarfs from the WISE All Sky data release using images obtained in filters that divide the traditional near-infrared H and J bands into two halves—specifically CH_(4s) and CH_4l in the H and J2, and J3 in the J. This proves to be very effective at identifying cool brown dwarfs via the detection of their methane absorption, as well as providing preliminary classification using methane colors and WISE -to-near-infrared colors. New and updated calibrations between T/Y spectral types and CH_(4s)–CH_4l J3–W2, and CH_(4s)–W2 colors are derived, producing classification estimates good to a few spectral sub-types. We present photometry for a large sample of T and Y dwarfs in these filters, together with spectroscopy for 23 new ultra-cool dwarfs—2 Y dwarfs and 21 T dwarfs. We identify a further 8 new cool brown dwarfs, which we have high confidence are T dwarfs based on their methane photometry. We find that, for objects observed on a 4 m class telescope at J-band magnitudes of ~20 or brighter, CH_(4s)–CH_4l is the more powerful color for detecting objects and then estimating spectral types. Due to the lower sky background in the J-band, the J3 and J2 bands are more useful for identifying fainter cool dwarfs at J ≳ 22. The J3–J2 color is poor at estimating spectral types. But fortunately, once J3–J2 confirms that an object is a cool dwarf, the J3–W2 color is very effective at estimating approximate spectral types.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Tinney, C. J.0000-0002-7595-0970
Kirkpatrick, J. Davy0000-0003-4269-260X
Faherty, Jacqueline K.0000-0001-6251-0573
Mace, Gregory N.0000-0001-7875-6391
Cushing, Mike0000-0001-7780-3352
Burgasser, Adam J.0000-0002-6523-9536
Sheppard, Scott S.0000-0003-3145-8682
Wright, Edward L.0000-0001-5058-1593
Additional Information:© 2018. The American Astronomical Society. Received 2017 December 27; revised 2018 March 26; accepted 2018 March 27; published 2018 May 17. C.G.T. gratefully acknowledges the support of ARC Australian Professorial Fellowship grant DP0774000 and ARC Discovery Outstanding Researcher Award DP130102695. We are grateful for the extraordinary support we have received from the AAT's technical staff—K. Fiegert, Y. Kondrat, S. Lee, R. Paterson, and D. Stafford. Australian access to the Magellan Telescopes was supported through the National Collaborative Research Infrastructure Strategy of the Australian Federal Government. Travel support for Magellan and AAT observing was provided by the Australian Astronomical Observatory. This publication makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration. This publication also makes use of data products from 2MASS, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. This research has made extensive use of the NASA/IPAC Infrared Science Archive (IRSA), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. This research has also benefitted from the M, L, and T dwarf compendium housed at, whose server was funded by a NASA Small Research Grant, administered by the American Astronomical Society. Facilities: AAT (IRIS2) - Anglo-Australian Telescope, Magellan:Baade (FourStar - , FIRE) - , Keck:II (NIRSPEC) - KECK II Telescope, IRTF (SpeX) - Infrared Telescope Facility, WISE - Wide-field Infrared Survey Explorer, CTIO:2MASS - 2MASS Telescope at Cerro Tololo Inter-American Observatory. Software: Figaro, FIREHOSE (, Spextool (Cushing et al. 2004), ORACDR (
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Australian Research CouncilDP0774000
Australian Research CouncilDP130102695
Australian Astronomical ObservatoryUNSPECIFIED
American Astronomical SocietyUNSPECIFIED
Subject Keywords:brown dwarfs; methods: observational; techniques: photometric
Issue or Number:2
Record Number:CaltechAUTHORS:20180518-114229345
Persistent URL:
Official Citation:C. G. Tinney et al 2018 ApJS 236 28
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:86452
Deposited By: George Porter
Deposited On:18 May 2018 19:45
Last Modified:15 Nov 2021 20:38

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