Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Probing the faint end of the quasar luminosity function at z ~ 4 in the
  COSMOS field   We searched for quasars that are ~ 3 mag fainter than the SDSS quasars in the
redshift range 3.7 < z < 4.7 in the COSMOS field to constrain the faint end of
the quasar luminosity function. Using optical photometric data, we selected 31
quasar candidates with 22 < i' < 24 at z ~ 4. We obtained optical spectra for
most of these candidates using FOCAS on the Subaru telescope, and identified 8
low-luminosity quasars at z ~ 4. In order to derive the quasar luminosity
function (QLF) based on our spectroscopic follow-up campaign, we estimated the
photometric completeness of our quasar survey through detailed Monte Carlo
simulations. Our QLF at z ~ 4 has a much shallower faint-end slope beta =
-1.67^{+0.11}_{-0.17} than that obtained by other recent surveys in the same
redshift. Our result is consistent with the scenario of downsizing evolution of
active galactic nuclei inferred by recent optical and X-ray quasar surveys at
lower redshifts.

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The categories of this paper are: nlin
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The categories of this paper are: adap-org
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The categories of this paper are: atom-ph
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The categories of this paper are: cond-mat
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The categories of this paper are: alg-geom
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The categories of this paper are: nucl-th
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The categories of this paper are: quant-ph
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The categories of this paper are: chem-ph
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The categories of this paper are: stat
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The categories of this paper are: eess
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The categories of this paper are: bayes-an
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The categories of this paper are: physics
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The categories of this paper are: hep-ex
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The categories of this paper are: hep-lat
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The categories of this paper are: patt-sol
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The categories of this paper are: q-fin