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Published July 1, 2007 | Published
Journal Article Open

Mid-Infrared Selection of Brown Dwarfs and High-Redshift Quasars


We discuss color selection of rare objects in a wide-field multiband survey spanning from the optical to the mid-infrared. Simple color criteria simultaneously identify and distinguish two of the most sought after astrophysical sources: the coolest brown dwarfs and the most distant quasars. We present spectroscopically confirmed examples of each class identified in the IRAC Shallow Survey of the Boötes field of the NOAO Deep Wide-Field Survey. IRAC J142950.8+333011 is a T4.5 brown dwarf at a distance of approximately 30-40 pc, and IRAC J142738.5+331242 is a radio-loud quasar at redshift z = 6.12. Our selection criteria identify a total of four candidates over 8 deg^2 of the Boötes field. The other two candidates are both confirmed 5.5 < z < 6 quasars, previously reported by Cool et al. (2006). We discuss the implications of these discoveries and conclude that there are excellent prospects for extending such searches to cooler brown dwarfs and higher redshift quasars.

Additional Information

© 2007 American Astronomical Society. Print publication: Issue 1 (2007 July 1); received 2006 August 25; accepted for publication 2006 November 15. We thank Chris Kochanek, Steve Willner, and the referee, Sandy Leggett, for useful comments on the manuscript. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology. Support was provided by NASA through an award issued by JPL/Caltech. This work also made use of images and/or data products provided by the NDWFS, which is supported by the National Optical Astronomy Observatory (NOAO). NOAO is operated by AURA, Inc., under a cooperative agreement with the National Science Foundation. A. D. and B. J. are supported by NOAO. We thank the staff of KPNO and Keck for their expert assistancewith our observations. Research has benefited from the M, L, and T dwarf compendium housed at http://DwarfArchives.org . The authors alsowish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community; we are most fortunate to have the opportunity to conduct observations from this mountain.

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