Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Integrated Relativistic Iron Line from Active Galactic Nuclei:
  Chasing the Spin Evolution of Supermassive Black Holes   The spin of a supermassive black hole (SMBH) is directly related to the
radiative efficiency of accretion on to the hole, and therefore impacts the
amount of fuel required for the black hole to reach a certain mass. Thus, a
knowledge of the SMBH spin distribution and evolution is necessary to develop a
comprehensive theory of the growth of SMBHs and their impact on galaxy
formation. Currently, the only direct measurement of SMBH spin is through
fitting the broad Fe K line in AGNs. The evolution of spins could be determined
by fitting the broad line in the integrated spectra of AGNs over different
redshift intervals. The accuracy of these measurements will depend on the
observed integrated line strength. Here, we present theoretical predictions of
the integrated relativistic Fe K line strength as a function of redshift and
AGN luminosity. The equivalent widths of the integrated lines are much less
than 300 eV. Searches for the integrated line will be easiest for unobscured
AGNs with 2-10 keV luminosities between 44 < log L_{X} <= 45. The total
integrated line makes up less than 4% of the X-ray background, but its shape is
sensitive to the average SMBH spin. By following these recommendations, future
International X-ray Observatory surveys of broad Fe K lines should be able to
determine the spin evolution of SMBHs.

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The categories of this paper are: chem-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: ao-sci
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The categories of this paper are: plasm-ph
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The categories of this paper are: math
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The categories of this paper are: econ
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The categories of this paper are: cs
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The categories of this paper are: cond-mat
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The categories of this paper are: physics
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The categories of this paper are: eess
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The categories of this paper are: chao-dyn
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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: funct-an
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The categories of this paper are: alg-geom
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The categories of this paper are: nucl-th