The cosmic X-ray background and the population of the most heavily obscured AGNs

Abstract

We report on an accurate measurement of the CXB in the 15-50 keV range performed with the Phoswich Detection System (PDS) instrument aboard the BeppoSAX satellite. We establish that the most likely CXB intensity level at its emission peak (26-28 keV) is ~40 keV/cm2/s/sr, a value consistent with that derived from the best available CXB measurement obtained over 25 years ago with the first High Energy Astronomical Observatory satellite mission (HEAO-1; Gruber et al. 1999), whose intensity, lying well below the extrapolation of some lower energy measurements performed with focusing telescopes, was questioned in the recent years. We find that 90% of the acceptable solutions of our best fit model to the PDS data give a 20-50 keV CXB flux lower than 6.5E-08 erg/cm2/s/sr, which is 12% higher than that quoted by Gruber et al. (1999) when we use our best calibration scale. This scale gives a 20-50 keV flux of the Crab Nebula of 9.22E-09 erg/cm2/s, which is in excellent agreement with the most recent Crab Nebula measurements and 6% smaller than that assumed by Gruber et al. (1999). In combination with the CXB synthesis models we infer that about 25% of the intensity at ~30 keV arises from extremely obscured, Compton thick AGNs (absorbing column density N_H > 1.0E+24 H/cm2), while a much larger population would be implied by the highest intensity estimates. We also infer a mass density of supermassive BHs of ~3.0E+05 Msol/Mpc3. The summed contribution of resolved sources (Moretti et al. 2003) in the 2-10 keV band exceeds our best fit CXB intensity extrapolated to lower energies, but it is within our upper limit, so that any significant contribution to the CXB from sources other than AGNs, such as star forming galaxies and diffuse Warm-Hot Intergalactic Medium (WHIM), is expected to be mainly confined below a few keV.

arXiv commentAccepted for publication in ApJ Main: 30 pages, 3 Tables, 8 Figures. Many revisions due to the change of the Journal

References in corpus (21)

• A Unified, Merger-Driven Model for the Origin of Starbursts, Quasars, the Cosmic X-Ray Background, Supermassive Black Holes and Galaxy Spheroids
• Cosmological Evolution of the Hard X-ray AGN Luminosity Function and the Origin of the Hard X-ray Background
• The synthesis of the cosmic X-ray background in the Chandra and XMM-Newton era
• The 2-10 keV luminosity as a Star Formation Rate indicator
• The HELLAS2XMM survey. VII. The hard X-ray luminosity function of AGN up to z=4: more absorbed AGN at low luminosities and high redshifts
• The Spectrum of Diffuse Cosmic Hard X-Rays Measured with HEAO-1
• The 2-8 keV cosmic X-ray background spectrum as observed with XMM-Newton
• X-ray background measurements with XMM-Newton EPIC
• Absolute measurement of the unresolved cosmic X-ray background in the 0.5-8 keV band with Chandra
• The resolved fraction of the Cosmic X-ray Background
• Study of the X-Ray Background Spectrum and its Large-Scale Fluctuation with ASCA
• INTEGRAL observations of the cosmic X-ray background in the 5-100 keV range via occultation by the Earth
• The spectrum of the cosmic X-ray background observed by RTXE/PCA
• Connecting Galaxy Evolution, Star Formation and the X-ray Background
• Extragalactic source counts in the 20-50 keV energy band from the deep observation of the Coma region by INTEGRAL/IBIS
• On the intensity of the cosmic X-ray background
• X-Ray Constraints on the Warm_hot Intergalactic Medium
• Intensity of the cosmic X-ray backgound from HEAO1/A2 experiment
• Can the unresolved X-ray background be explained by emission from the optically-detected faint galaxies of the GOODS project?
• The X-ray background and the deep X-ray surveys
• The Missing X-ray Background

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