Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Ultracool Field Brown Dwarf Candidates Selected at 4.5 microns   We have identified a sample of cool field brown dwarf candidates using IRAC
data from the Spitzer Deep, Wide-Field Survey (SDWFS). The candidates were
selected from 400,000 SDWFS sources with [4.5] <= 18.5 mag and required to have
[3.6]-[4.5] >= 1.5 and [4.5] - [8.0] <= 2.0 on the Vega system. The first color
requirement selects objects redder than all but a handful of presently known
brown dwarfs with spectral classes later than T7, while the second eliminates
14 probable reddened AGN. Optical detection of 4 of the remaining 18 sources
implies they are likely also AGN, leaving 14 brown dwarf candidates. For two of
the brightest candidates (SDWFS J143524.44+335334.6 and SDWFS
J143222.82+323746.5), the spectral energy distributions including near-infrared
detections suggest a spectral class of ~ T8. The proper motion is < 0.25 "/yr,
consistent with expectations for a luminosity inferred distance of >70 pc. The
reddest brown dwarf candidate (SDWFS J143356.62+351849.2) has [3.6] -
[4.5]=2.24 and H - [4.5] > 5.7, redder than any published brown dwarf in these
colors, and may be the first example of the elusive Y-dwarf spectral class.
Models from Burrows et al. (2003) predict larger numbers of cool brown dwarfs
should be found for a Chabrier (2003) mass function. Suppressing the model
[4.5] flux by a factor of two, as indicated by previous work, brings the
Burrows models and observations into reasonable agreement. The recently
launched Wide-field Infrared Survey Explorer (WISE) will probe a volume ~40x
larger and should find hundreds of brown dwarfs cooler than T7.

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The categories of this paper are: hep-th
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The categories of this paper are: econ
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The categories of this paper are: nucl-th
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The categories of this paper are: adap-org
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The categories of this paper are: comp-gas
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The categories of this paper are: math-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: gr-qc
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The categories of this paper are: patt-sol
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The categories of this paper are: alg-geom
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The categories of this paper are: nucl-ex
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The categories of this paper are: solv-int
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The categories of this paper are: chao-dyn
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The categories of this paper are: cs
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The categories of this paper are: hep-ex
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The categories of this paper are: atom-ph