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INTEGRAL/IBIS all-sky survey in hard X-rays

INTEGRAL/IBIS all-sky survey in hard X-rays

Publication date: 15 November 2007

Authors: Krivonos, R. et al.

Journal: Astronomy & Astrophysics
Volume: 475
Issue: 2
Page: 775-784
Year: 2007

Copyright: ESO

We present results of an all-sky hard X-ray survey based on almost four years of observations with the IBIS telescope onboard the INTEGRAL observatory. The dead time-corrected exposure of the survey is ~33 Ms. Approximately 12% and 80% of the sky has been covered to limiting fluxes lower than 1 and 5 mCrab, respectively. Our catalog of detected sources includes 403 objects, 316 of which exceed a 5-sigma detection threshold on the time-averaged map of the sky, and the rest were detected in various subsamples of exposures. Among the identified sources, 219 are Galactic (90 low-mass X-ray binaries, 76 high-mass X-ray binaries, 21 cataclysmic variables, 6 coronally active stars, and other types) and 137 are extragalactic, including 130 active galactic nuclei (AGNs) and 3 galaxy clusters. We derived number-flux functions of AGNs and Galactic sources. The log N-log S relation of non-blazar AGNs is based on 68 sources located at Galactic latitudes |b| > 5°, where the survey is characterized by high identification completeness, with fluxes higher than Slim = 1.1 × 10-11 erg s-1 cm-2 (~0.8 mCrab) in the 17-60 keV energy band. The cumulative AGN number-flux function can be described by a power law with a slope of 1.62 ± 0.15 and normalization of (5.7±0.7) × 10-3 sources per deg² at fluxes > 1.43 × 10-11 erg s-1 cm-2 (>1 mCrab). Those AGNs with fluxes higher than Slim make up ~1% of the cosmic X-ray background at 17-60 keV. We present evidence of strong inhomogeneity in the spatial distribution of nearby (<70 Mpc) AGNs, which reflects the large-scale structure in the local Universe.

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