Book contents
- Frontmatter
- Contents
- Index of Participants
- Preface
- I Evidence and Implications of Anisotropy in AGN
- II Luminosity Functions and Continuum Energy Distributions
- Radio Luminosity Functions of Active Galaxies
- The Quasar Luminosity Function
- UK ROSAT Deep & Extended Deep Surveys
- Luminosity Dependence of Optical Activity in Radio Galaxies
- Modelling the Quasar Luminosity Function in Hierarchical Models for Structure Formation
- Active Galactic Nuclei in Clusters of Galaxies
- Clustering Properties of AGNs and their Contribution to the X-ray Background
- Energy Distributions of AGN
- Absorption in the ROSAT X-ray Spectra of Quasars
- Dust in AGNs
- First Simultaneous UBVRI Photopolarimetric Observations of a Sample of Normal Quasars
- Intermediate Resolution Spectropolarimetry of Three Quasars
- Active Galaxies which Emit Strongly at 25μm
- III The Broad Line Region: Variability and Structure
- IV X-rays and Accretion Disks
- V Beams, Jets and Blazars
- VI Concluding Talk
Clustering Properties of AGNs and their Contribution to the X-ray Background
from II - Luminosity Functions and Continuum Energy Distributions
Published online by Cambridge University Press: 04 August 2010
- Frontmatter
- Contents
- Index of Participants
- Preface
- I Evidence and Implications of Anisotropy in AGN
- II Luminosity Functions and Continuum Energy Distributions
- Radio Luminosity Functions of Active Galaxies
- The Quasar Luminosity Function
- UK ROSAT Deep & Extended Deep Surveys
- Luminosity Dependence of Optical Activity in Radio Galaxies
- Modelling the Quasar Luminosity Function in Hierarchical Models for Structure Formation
- Active Galactic Nuclei in Clusters of Galaxies
- Clustering Properties of AGNs and their Contribution to the X-ray Background
- Energy Distributions of AGN
- Absorption in the ROSAT X-ray Spectra of Quasars
- Dust in AGNs
- First Simultaneous UBVRI Photopolarimetric Observations of a Sample of Normal Quasars
- Intermediate Resolution Spectropolarimetry of Three Quasars
- Active Galaxies which Emit Strongly at 25μm
- III The Broad Line Region: Variability and Structure
- IV X-rays and Accretion Disks
- V Beams, Jets and Blazars
- VI Concluding Talk
Summary
Introduction
The Autocorrelation Function (ACF) of the intensity fluctuations of the X-ray background (XRB) is an integrated view of the clustering properties of the source populations contributing to the XRB, so studies of the ACF provide information on the origin of the XRB as well as on clustering evolution of the underlying sources.
Recently ROSAT Deep Surveys have shown that about 40% of the soft XRB (E ≤ 3keV, henceforth SXRB) is contributed by sources brighter than S(0.5–2keV) ≥ 7 × 10−15 erg s−1 cm−2 (Hasinger et al. 1991; Shanks et al. 1991). On the other hand only a few percent of the hard XRB (3 < E < 60keV, henceforth HXRB) has already been resolved into sources. ROSAT observations also show that the SXRB is actually very smooth on arcminute scales with a current upper limit on the ACF in the 0.9–2.4keV band W(9′) ≤ 2 × 10−3 (Hasinger 1992). As regards the HXRB, the results of the ACF analyses on sub-degree angular scales have been used to put significant constraints on clustering of AGNs and galaxy clusters (Martín-Mirones et al. 1991; Carrera et al. 1992). Here we will discuss data on ACFs to obtain limits on clustering, clustering evolution and volume emissivity of X-ray sources contributing to the SXRB and HXRB.
Constraints on the clustering scale and the clustering evolution of AGNs and on their contribution to the XRB
Recent analyses of large samples of optically selected QSOs have produced consistent values of the clustering scale, 12 ≲ r0 ≲ 20 Mpc (H0 = 50kms−1 Mpc−1), and of the evolution of the correlation function with ∈ ≥ −1.2, a constant comoving clustering scale being slightly favoured (Boyle 1991; Andreani & Cristiani 1992).
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- The Nature of Compact Objects in Active Galactic NucleiProceedings of the 33rd Herstmonceux Conference, held in Cambridge, July 6-22, 1992, pp. 129 - 130Publisher: Cambridge University PressPrint publication year: 1994