Kakazu, Yuko and Hu, Esther M. and Liu, Michael C. and Wang, Wei-Hao and Wainscoat, Richard J. and Capak, Peter L. (2010) Hawaii quasar and T dwarf survey. I. Method and discovery of faint field ultracool dwarfs. Astrophysical Journal, 723 (1). pp. 184-196. ISSN 0004-637X. http://resolver.caltech.edu/CaltechAUTHORS:20101214-135434627
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The Hawaii Quasar and T dwarf survey (HQT Survey) is a wide-field, red optical survey carried out with the Suprime-Cam mosaic CCD camera on the 8.2 m Subaru telescope. The HQT survey is designed to search for low-luminosity (M_(AB1450) < −23) quasars at high redshift (z > 5.7) as well as T dwarfs, both of which are selected by their very red I − z' colors. We use an optical narrowband filter NB816 to break a well-known I − z' color degeneracy between high-z quasars and foreground M and L dwarfs, which are more numerous than quasars. This paper is the first in a series of papers from the HQT survey and we report on the discovery of six faint (19 ≤ J ≤ 20) ultracool dwarfs found over a ~9.3 deg^2 area with a limiting magnitude of z'_(AB) ≤ 23.3. These dwarfs were confirmed by near-IR imaging and/or spectroscopy conducted at various facilities on Mauna Kea. With estimated distances of 60–170 pc, these are among the most distant spectroscopically confirmed field brown dwarfs to date. Limits on the proper motions of these ultracool dwarfs suggest that they are old members of the Galactic disk, though future follow-up observations are necessary to minimize errors. Our finding rate of ultracool dwarfs is within model predictions of Liu et al. However, the large brightening amplitude (~1 mag) previously reported for the L/T transition objects appears to overpredict the numbers. We also examine how the survey field latitude affects the survey sensitivity to the vertical scale height of ultracool dwarfs.
|Additional Information:||© 2010 American Astronomical Society. Received 2009 August 7; accepted 2010 March 3; published 2010 October 8. Based in part on data obtained at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan. Based in part on data obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA and was made possible by the generous financial support of the W. M. Keck Foundation. We are indebted to the staff of the Subaru, Keck, and UKIRT observatories for their excellent assistance with the observations. We especially thank the support astronomer, Hisanori Furusawa, for his invaluable help in completing the observing run with the Suprime-Cam. We are also grateful to the anonymous referee for a helpful report.|
|Subject Keywords:||brown dwarfs, early universe, quasars: general, stars: low-mass, techniques: photometric|
|Classification Code:||PACS: 95.80.+p; 97.20.Vs; 98.62.Hr; 98.54.Aj; 98.62.Lv; 98.62.Py|
|Official Citation:||Yuko Kakazu et al 2010 ApJ 723 184 doi: 10.1088/0004-637X/723/1/184|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Benjamin Perez|
|Deposited On:||14 Dec 2010 22:42|
|Last Modified:||06 Jul 2015 20:28|
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