Can we reproduce the X-ray background spectral shape using local AGN?

Abstract

The X-ray background (XRB) is due to the aggregate of active galactic nuclei (AGN), which peak in activity at z~1 and is often modeled as the sum of different proportions of unabsorbed, moderately- and heavily-absorbed AGN. We present the summed spectrum of a complete sample of local AGN (the Northern Galactic Cap of the 58-month Swift/BAT catalog, z<0.2) using 0.4-200keV data and directly determine the different proportions of unabsorbed, moderately and heavily-absorbed AGN that make up the summed spectrum. This stacked low redshift AGN spectrum is remarkably similar in shape to the XRB spectrum (when shifted to z~1), but the observed proportions of different absorption populations differ from most XRB synthesis models. AGN with Compton-thick absorption account for only ~12% of the sample, but produce a significant contribution to the overall spectrum. We confirm that Compton reflection is more prominent in moderately-absorbed AGN and that the photon index differs intrinsically between unabsorbed and absorbed AGN. The AGN in our sample account for only ~1% of the XRB intensity. The reproduction of the XRB spectral shape suggests that strong evolution in individual AGN properties is not required between z~0 and 1.

6 pages, 5 figures, accepted for publication in ApJ Letters

References in corpus (7)

• The synthesis of the cosmic X-ray background in the Chandra and XMM-Newton era
• Cosmic X-ray background and Earth albedo Spectra with Swift/BAT
• INTEGRAL observations of the cosmic X-ray background in the 5-100 keV range via occultation by the Earth
• Cumulative hard X-ray spectrum of local AGN: a link to the cosmic X-ray background
• Constraints on light bending and reflection from the hard X-ray background
• Can the unresolved X-ray background be explained by emission from the optically-detected faint galaxies of the GOODS project?
• The redshift distribution of the X-ray background

Cited by in corpus (30)

• BAT AGN Spectroscopic Survey - V. X-ray properties of the Swift/BAT 70-month AGN catalog
• Compton-thick Accretion in the local Universe
• The observable signature of late heating of the Universe during cosmic reionization
• The Swift/BAT AGN Spectroscopic Survey (BASS) -- VI. The Gamma_X - L/L_Edd relation
• The Rise of the First Stars: Supersonic Streaming, Radiative Feedback, and 21-cm Cosmology
• Long-term variability of AGN at hard X-rays
• Iron K$\alpha$ emission in type-I and type-II Active Galactic Nuclei
• NuSTAR unveils a Compton-thick Type 2 quasar in Mrk 34
• The NuSTAR Extragalactic Surveys: The Number Counts of Active Galactic Nuclei and the Resolved Fraction of the Cosmic X-ray Background
• A selection effect boosting the contribution from rapidly spinning black holes to the Cosmic X-ray Background
• Compton-Thick AGN in the NuSTAR era VI: The observed Compton-thick fraction in the Local Universe
• The NuSTAR Extragalactic Surveys: Initial Results and Catalog from the Extended Chandra Deep Field South
• The narrow Fe K$\alpha$ line and the molecular torus in active galactic nuclei - an IR/X-ray view
• NuSTAR observations of heavily obscured Swift/BAT AGN: constraints on the Compton-thick AGN fraction
• The average 0.5-200 keV spectrum of local active galactic nuclei and a new determination of the 2-10 keV luminosity function at z \approx 0
• The column density distribution of hard X-ray radio galaxies
• The NuSTAR Extragalactic Survey: Average broad-band X-ray spectral properties of the NuSTAR detected AGN
• NuSTAR view of Swift/BAT AGN: The $R$-$\Gamma$ correlation
• Study of X-ray variability and coronae of Seyfert galaxies using NuSTAR
• Comparing the host galaxy ages of X-ray selected AGN in COSMOS: Obscured AGN are associated with older galaxies
• Mildly obscured active galaxies and the cosmic X-ray background
• Investigating the Covering Fraction Distribution of Swift/BAT AGN with X-ray and IR Observations
• The NuSTAR Extragalactic Survey of the James Webb Space Telescope North Ecliptic Pole Time-Domain Field
• Compton-thick AGN in the NuSTAR Era X: Analysing seven local CT-AGN candidates
• Broad-band X-ray analysis of local mid-infrared selected Compton-thick AGN candidates
• Towards a complete census of luminous Compton-thick Active Galactic Nuclei in the local Universe
• NuSTAR spectral analysis of three Seyfert galaxies: NGC 3227, NGC 5548 and MR 2251$-$178
• The source number counts at high energies: SWIFT vs. NuSTAR
• NuSTAR view of heavily absorbed AGN: The $R-N_{\text{H}}$ correlation
• NuSTAR reveals that the heavily obscured nucleus of NGC 2785 was the contaminant of IRAS 09104+4109 in the BeppoSAX/PDS hard X-rays