Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Luminosity-dependent evolution of soft X-ray selected AGN: New Chandra
  and XMM-Newton surveys   We present new results on the cosmological evolution of unabsorbed (type-1)
active galactic nuclei (AGN) selected in the soft (0.5-2 keV) X-ray band. From
a variety of ROSAT, XMM-Newton and Chandra surveys we selected a total of ~1000
AGN with an unprecedented spectroscopic and photometric optical/NIR
identification completeness. For the first time we are able to derive reliable
space densities for low-luminosity (Seyfert-type) X-ray sources at cosmological
redshifts. The evolutionary behaviour of AGN shows a strong dependence on X-ray
luminosity: while the space density of high-luminosity AGN reaches a peak
around z~2, similar to that of optically selected QSO, the space density of
low-luminosity AGNs peaks at redshifts below z=1. This confirms previous ROSAT
findings of a luminosity-dependent density evolution. Using a rigorous
treatment of the optical identification completeness we are able to show that
the space density of AGN with X-ray luminosities L_x < 10^45 erg s^-1 declines
significantly towards high redshifts.

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The categories of this paper are: quant-ph
2
The categories of this paper are: math
32
The categories of this paper are: atom-ph
28
The categories of this paper are: alg-geom
9
The categories of this paper are: nlin
22
The categories of this paper are: chao-dyn
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The categories of this paper are: acc-phys
0
The categories of this paper are: hep-ph
33
The categories of this paper are: plasm-ph
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The categories of this paper are: eess
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The categories of this paper are: nucl-th
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The categories of this paper are: funct-an
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The categories of this paper are: math-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: cs
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The categories of this paper are: mtrl-th