The redshift distribution of the X-ray background

Abstract

The X-ray background (XRB) is produced by a large number of faint sources distributed over a wide range of redshifts. The XRB carries information on the spatial distribution and evolution of these sources. The goals of the paper are: 1. to determine the redshift distribution of the soft X-ray background photons produced by all types of extragalactic sources, in order to relate fluctuations of the background to the large scale structures, 2. to determine the redshift distribution of the soft XRB produced by AGN in order to calculate the evolution of the AGN X-ray luminosity density. A set of major X-ray surveys is used to determine the redshift distributions of the X-ray sources selected at various flux levels. Simple analytic fits to the data allow us to determine the smooth relationship between the redshift distribution and the source flux. The redshift distribution of the integral XRB flux is obtained by averaging the fits over the source counts. It is shown that the distribution of extragalactic XRB photons in the 0.5-2 keV band is adequately represented by the function: dn/dlog z = 5.24 z^1.52 exp(-z/0.63). The huge voids postulated to explain the cold spots in the CMB maps create dips in the total XRB flux. However, the expected magnitude of the effect is comparable to the fluctuation amplitude of the XRB generated by the individual sources contributing to the background. The cosmic evolution of the AGN X-ray luminosity density up to redshift of ~5 is calculated in an elegant and straightforward way. Systematic uncertainties of the present method are assessed and shown to be small. At redshift greater than one the present results could be compared directly with some recent estimates obtained in a standard way and the agreement between both methods is very good.

13 pages, 4 figures, submitted to AA

References in corpus (22)

• The Chandra Deep Field-North Survey. XIII. 2 Ms Point-Source Catalogs
• Luminosity-dependent evolution of soft X-ray selected AGN: New Chandra and XMM-Newton surveys
• The Chandra Deep Field South: the 1 Million Second
• The Chandra Deep Field South: Optical Spectroscopy I
• Deep Extragalactic X-ray Surveys
• The resolved fraction of the Cosmic X-ray Background
• Optical and Infrared Properties of the 2 Ms Chandra Deep Field-North X-ray Sources
• A Spectroscopic Survey of Redshift 1.4<z<3.0 Galaxies in the Goods-North Field: Survey Description, Catalogs, and Properties
• X-ray, Optical, and Infrared Imaging and Spectral Properties of the 1 Ms Chandra Deep Field North Sources
• Spitzer Power-law AGN Candidates in the Chandra Deep Field-North
• Extragalactic Radio Sources and the WMAP Cold Spot
• The ROSAT Deep Survey: VI. X-ray sources and Optical identifications of the Ultra Deep Survey
• Tracing the large scale structure in the Chandra Deep Field South
• A Flux-limited Sample of Bright Clusters of Galaxies from the Southern Part of the ROSAT All-Sky Survey: the Catalog and the LogN-LogS
• 531 new spectroscopic redshifts from the CDFS and a test on the cosmological relevance of the GOODS-South field
• Chandra Multiwavelength Project X-ray Point Source Number Counts and the Cosmic X-ray Background
• Photometric Redshift of X-Ray Sources in the Chandra Deep Field South
• The ROSAT North Ecliptic Pole Survey: The X-ray Catalog
• The ROSAT North Ecliptic Pole Survey: The Optical Identifications
• The North Ecliptic Pole Supercluster
• X-ray selected starbursts in the GOODS-North
• The Properties and Redshift Evolution of Intermediate-Luminosity Off-Nuclear X-ray Sources in the Chandra Deep Fields

Cited by in corpus (2)

• Can we reproduce the X-ray background spectral shape using local AGN?
• What X-ray source counts can tell about large-scale matter distribution