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Date and Time of the Query: 2019-04-18 T03:50:54 PDT
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For refcode 2007A&A...462...57S:
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Copyright by European Southern Observatory (ESO). Reproduced by permission
2007A&A...462...57S Hard X-ray luminosity function and absorption distribution of nearby AGN: INTEGRAL all-sky survey Sazonov, S.; Revnivtsev, M.; Krivonos, R.; Churazov, E.; Sunyaev, R. Abstract. Aims. We study the hard X-ray luminosity function and absorption distribution of local (z<~ 0.1) 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 (>5{sigma}) 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 |b|>5^degree^, 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 f_a_ of obscured (logN_H>22) objects is much higher (~ 70%) among the low-luminosity AGN (L_hx<10^43.6^ erg s^-1^) than among the high-luminosity ones (L_hx>10^43.6^ erg s^-1^), f_a~ 25%, where L_hx 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 ~ 10^40^-10^41^ 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 40<logL_hx<45.5 with a characteristic luminosity of logL_*=43.40+/- 0.28. The estimated local luminosity density due to AGN with logL_hx>40 is (1.4+/- 0.3)x 10^39^ 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 N_H_ distribution of AGN (for a given L_hx/L_*(z) ratio) has not changed significantly since z~ 1.5, while the AGN luminosity function has experienced pure luminosity evolution. Key words: surveys, galaxies: active, galaxies: evolution, galaxies: Seyfert, X-rays: diffuse background
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