Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Cumulative hard X-ray spectrum of local AGN: a link to the cosmic X-ray
  background   We determine the cumulative spectral energy distribution (SED) of local AGN
in the 3-300 keV band and compare it with the spectrum of the cosmic X-ray
background (CXB) in order to test the widely accepted paradigm that the CXB is
a superposition of AGN and to place constraints on AGN evolution. We performed
a stacking analysis of the hard X-ray spectra of AGN detected in two recent
all-sky surveys, performed by the IBIS/ISGRI instrument aboard INTEGRAL and by
the PCA instrument aboard RXTE, taking into account the space densities of AGN
with different luminosities and absorption column densities. We derived the
collective SED of local AGN in the 3-300 keV energy band. Those AGN with
luminosities below 10^43.5 erg/s (17-60 keV) provide the main contribution to
the local volume hard X-ray emissivity, at least 5 times more than more
luminous objects. The cumulative spectrum exhibits (although with marginal
significance) a cutoff at energies above 100-200 keV and is consistent with the
CXB spectrum if AGN evolve over cosmic time in such a way that the SED of their
collective high-energy emission has a constant shape and the relative fraction
of obscured AGN remains nearly constant, while the AGN luminosity density
undergoes strong evolution between z~1 and z=0, a scenario broadly consistent
with results from recent deep X-ray surveys. The first direct comparison
between the collective hard X-ray SED of local AGN and the CXB spectrum
demonstrates that the popular concept of the CXB being a superposition of AGN
is generally correct. By repeating this test using improved AGN statistics from
current and future hard X-ray surveys, it should be possible to tighten the
constraints on the cosmic history of black hole growth.

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The categories of this paper are: quant-ph
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The categories of this paper are: supr-con
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The categories of this paper are: physics
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The categories of this paper are: solv-int
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The categories of this paper are: hep-lat
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The categories of this paper are: dg-ga
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The categories of this paper are: q-bio
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The categories of this paper are: hep-ex
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The categories of this paper are: nlin
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The categories of this paper are: hep-ph
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The categories of this paper are: hep-th
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The categories of this paper are: econ
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The categories of this paper are: cond-mat
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The categories of this paper are: nucl-th
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The categories of this paper are: math
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The categories of this paper are: nucl-ex