Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Mid-infrared spectroscopy of high-redshift obscured quasars   We present mid-infrared observations of 18 sources from a sample of 21 z~2
radio-intermediate obscured quasars. The mid-infrared spectra of the sources
are continuum dominated, and 12 sources show deep silicate absorption with
tau_9.7~1-2. Combining mid-infrared and optical spectra, we achieve 86%
spectroscopic completeness which allows us to confirm that most (63 +14 -22 %)
z~2 radio-intermediate quasars are obscured. The new spectra also prove that
many high-redshift type-2 quasars do not show any rest-frame ultraviolet
emission lines. From the 18 individual mid-infrared spectra, we classify most
of the sources into three subsamples: those with hints of the 7.7 and 6.2
micron polyaromatic hydrocarbons (3/18 sources show PAHs, subsample A), those
with an excess of emission around 8 micron but no hint of the 6.2 micron PAH
(7/18 cases, subsample B) and pure-continuum sources with no visible excess
(4/18 sources, subsample C). The remaining 4/18 sources have spectra that are
featureless or too noisy for any features to be visible. In subsample A,
averaging the spectra leads to a statistical detection of both 6.2 and 7.7
micron PAHs over the continuum, with the strength of the 7.7 micron PAH
comparable to that of submillimetre-selected galaxies (SMGs) at similar
redshifts. These sources are in a phase of coeval growth of a supermassive
black hole and a host galaxy.

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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-ex
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The categories of this paper are: solv-int
37
The categories of this paper are: supr-con
1
The categories of this paper are: cs
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The categories of this paper are: econ
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The categories of this paper are: alg-geom
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The categories of this paper are: dg-ga
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The categories of this paper are: stat
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The categories of this paper are: math-ph
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The categories of this paper are: math
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The categories of this paper are: ao-sci
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The categories of this paper are: hep-th
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The categories of this paper are: chem-ph
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The categories of this paper are: adap-org
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The categories of this paper are: cmp-lg