A deep INTEGRAL hard X-ray survey of the 3C 273/Coma region

Abstract

(abridged) We present an analysis of the deepest hard X-ray survey to date of about 2500 deg^2 performed by the IBIS instrument on board INTEGRAL in the 20-60 keV band, with a total exposure time of 4 Ms. We find 34 candidate sources. The ratio of Seyfert 1 to Seyfert 2 is significantly more than the ratio found in the optical, which may be evidence for a receding torus, but could also be due to absorption columns > 10^{25} cm^{-2}. None of the predicted Compton-thick objects is detected unambiguously; when taking lower limits on Nh into account, the fraction of these objects is found to be lower than 24%. We do not see, but cannot exclude, a relationship between absorption and luminosity similar to what is seen in the 2-10 keV band. Our data suggests the possibility of a lack of objects with 10^{21} < Nh < 10^{22} cm^{-2}, as expected if absorption originates either in a torus-like structure or in the host galaxy. We find that the Log N-Log S diagram of our sources is compatible with those obtained in other surveys in hard X-rays. Compared to models of the AGN population selected in the 2-10 keV band, the Log N-Log S diagram is generally in good agreement, but the Nh distribution is significantly different, with significantly less unabsorbed sources (Nh<10^{22} cm^{-2}) at a given flux limit compared to the models. We resolve here about 2.5% of the cosmic X-ray background. We also study the local hard X-ray luminosity function, which is compatible with what is found in other recent hard X-ray surveys. The characteristic luminosity Log L*_{20-60 keV}=43.66 is found to be a factor about 5 lower than the value observed in the 2-10 keV band. We find a space density of 10^{-3} AGN with L>10^{41} per Mpc^3 and a corresponding luminosity density of 0.9 10^{39} erg s^{-1} Mpc^{-3}.

12 pages, accepted for publication in A&A

References in corpus (10)

• The synthesis of the cosmic X-ray background in the Chandra and XMM-Newton era
• The Luminosity Function of X-ray Selected Active Galactic Nuclei: Evolution of Supermassive Black Holes at High Redshift
• INTEGRAL observations of the cosmic X-ray background in the 5-100 keV range via occultation by the Earth
• Investigating on the nuclear obscuration in two types of Seyfert 2 galaxies
• The distribution of absorption in AGN detected in the XMM-Newton observations of the CDFS
• Unveiling the nature of INTEGRAL objects through optical spectroscopy. IV. A study of six new hard X-ray sources
• Spectral Statistics and Local Luminosity Function of a Hard X-ray Complete Sample of Brightest AGNs
• The AGN nature of 11 out of 12 Swift/RXTE unidentified sources through optical and X-ray spectroscopy
• The Deep Chandra Survey of the Groth Strip - II. optical identification of the X-ray sources
• South-West extension of the hard X-ray emission from the Coma cluster

Cited by in corpus (9)

• BAT AGN Spectroscopic Survey - V. X-ray properties of the Swift/BAT 70-month AGN catalog
• BASS XXXVII: The role of radiative feedback in the growth and obscuration properties of nearby supermassive black holes
• Hard X-ray identification of Eta Carinae and steadiness close to periastron
• INTEGRAL 11-year hard X-ray survey above 100 keV
• 15 years of Galactic surveys and hard X-ray Background measurements
• Reconstructing AGN X-ray spectral parameter distributions with Bayesian methods II: Population inference
• The hard X-ray view of bright infrared galaxies
• The properties of the Galactic Hard X-Ray and soft gamma-ray Background based on 20 years of INTEGRAL/IBIS observations
• Self-consistent population synthesis of AGN from observational constraints in the X-rays