Issue |
A&A
Volume 462, Number 1, January IV 2007
|
|
---|---|---|
Page(s) | 57 - 66 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361:20066277 | |
Published online | 02 November 2006 |
Hard X-ray luminosity function and absorption distribution of nearby AGN: INTEGRAL all-sky survey
1
Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85740 Garching bei München, Germany e-mail: sazonov@mpa-garching.mpg.de
2
Space Research Institute, Russian Academy of Sciences, Profsoyuznaya 84/32, 117997 Moscow, Russia
Received:
20
August
2006
Accepted:
24
September
2006
Aims.We study the hard X-ray luminosity function and absorption
distribution of local () active galactic nuclei
(AGN) and discuss the implications for AGN cosmological evolution
and for the cosmic X-ray background (CXB).
Methods.We use the INTEGRAL all-sky hard X-ray survey to perform a
statistical study of a representative sample of nearby AGN. Our
entire all-sky sample consists of 127 AGN, of which 91 are
confidently detected (>) on the time-averaged map obtained
with the IBIS/ISGRI instrument and 36 are detected only during
single observations. Among the former there are 66 non-blazar AGN
located at
, where the survey's identification
completeness is ∼93%, which we use
for calculating the AGN luminosity function and X-ray
absorption distribution.
Results.In broad agreement with previous studies, we find that the fraction
fa of obscured (log) objects is much higher (~
%) among the low-luminosity AGN (
erg s-1)
than among the high-luminosity ones (
erg s-1),
%, where Lhx is the luminosity in the
17–60 keV energy band. We also find that locally the fraction of
Compton-thick AGN is less than 20% unless there is a significant
population of AGN that are so strongly obscured that their observed hard
X-ray luminosities fall below ~
1040–1041 erg s-1, the effective limit of our
survey. The constructed hard X-ray luminosity function has a
canonical, smoothly broken power-law shape in the range
log
with a characteristic luminosity of
log
. The estimated local luminosity density due
to AGN with log
is
erg s-1 Mpc-3 (17–60 keV). We demonstrate that
the spectral shape and amplitude of the CXB are consistent with the
simple scenario in which the NH distribution of AGN (for a given
ratio) has not changed significantly since
,
while the AGN luminosity function has experienced pure luminosity evolution.
Key words: surveys / galaxies: active / galaxies: evolution / galaxies: Seyfert / X-rays: diffuse background
© ESO, 2007
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