Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Parkes quarter-Jansky flat-spectrum sample 3. Space density and
  evolution of QSOs   We analyze the Parkes quarter-Jansky flat-spectrum sample of QSOs in terms of
space density, including the redshift distribution, the radio luminosity
function, and the evidence for a redshift cutoff. With regard to the luminosity
function, we note the strong evolution in space density from the present day to
epochs corresponding to redshifts ~ 1. We draw attention to a selection effect
due to spread in spectral shape that may have misled other investigators to
consider the apparent similarities in shape of luminosity functions in
different redshift shells as evidence for luminosity evolution. To examine the
evolution at redshifts beyond 3, we develop a model-independent method based on
the V_max test using each object to predict expectation densities beyond z=3.
With this we show that a diminution in space density at z > 3 is present at a
significance level >4 sigma. We identify a severe bias in such determinations
from using flux-density measurements at epochs significantly later than that of
the finding survey. The form of the diminution is estimated, and is shown to be
very similar to that found for QSOs selected in X-ray and optical wavebands.
The diminution is also compared with the current estimates of star-formation
evolution, with less conclusive results. In summary we suggest that the
reionization epoch is little influenced by powerful flat-spectrum QSOs, and
that dust obscuration does not play a major role in our view of the QSO
population selected at radio, optical or X-ray wavelengths.

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The categories of this paper are: hep-th
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The categories of this paper are: nucl-ex
11
The categories of this paper are: hep-lat
35
The categories of this paper are: mtrl-th
20
The categories of this paper are: acc-phys
23
The categories of this paper are: solv-int
36
The categories of this paper are: cmp-lg
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The categories of this paper are: eess
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The categories of this paper are: math-ph
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The categories of this paper are: dg-ga
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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: cond-mat
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The categories of this paper are: comp-gas
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The categories of this paper are: nucl-th
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The categories of this paper are: chao-dyn