Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A slitless spectroscopic survey for quasars near quasars   We present the results of the Quasars near Quasars (QNQ) survey, a CCD-based
slitless spectroscopic survey for faint V<22 quasars at 1.7<z<3.6 on 18
26.2'x33.5' fields centred on bright quasars at 2.76<z<4.69. In total 169
quasar candidates with emission lines were selected from the extracted
flux-calibrated spectra on the basis of well-defined automatic selection
criteria followed by visual inspection and verification. With follow-up
spectroscopy of 81 candidates that were likely to reside at z>1.7 we were able
to confirm 80 new quasars at 0.580<z<3.586 on 16 of our fields. 64 of the newly
discovered quasars are located at z>1.7. The overall high success rate implies
that most of the remaining 88 candidates are quasars as well, although the
majority of them likely resides at z<1.7 on the basis of the observed line
shapes and strengths. Due to the insufficient depth of the input source
catalogues needed for extraction of the slitless spectra our survey is not well
defined in terms of limiting magnitude for faint 2.5<z<3.6 quasars whose Lyman
alpha emission is detectable well beyond V=22, albeit at a continuum S/N<1.
While not useful for characterising the evolving space density of quasars, our
sample provides many new closely spaced quasar sightlines around intensely
studied quasars for further investigations on the three-dimensional
distribution of the intergalactic medium.

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The categories of this paper are: nlin
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The categories of this paper are: cond-mat
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The categories of this paper are: hep-ph
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The categories of this paper are: math-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: stat
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The categories of this paper are: patt-sol
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The categories of this paper are: eess
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The categories of this paper are: chem-ph
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The categories of this paper are: funct-an
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The categories of this paper are: hep-th
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The categories of this paper are: q-bio
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The categories of this paper are: q-fin
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The categories of this paper are: hep-ex
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The categories of this paper are: acc-phys
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The categories of this paper are: econ