Volume 462, Number 1, January IV 2007
|Page(s)||57 - 66|
|Published online||02 November 2006|
Hard X-ray luminosity function and absorption distribution of nearby AGN: INTEGRAL all-sky survey
Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85740 Garching bei München, Germany e-mail: email@example.com
2 Space Research Institute, Russian Academy of Sciences, Profsoyuznaya 84/32, 117997 Moscow, Russia
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
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.