Can AGN and galaxy clusters explain the surface brightness fluctuations of the cosmic X-ray background?

Abstract

Fluctuations of the surface brightness of cosmic X-ray background (CXB) carry unique information about faint and low luminosity source populations, which is inaccessible for conventional large-scale structure (LSS) studies based on resolved sources. We used Chandra data of the XBOOTES field ($\sim 9\mathrm{de}{\mathrm{g}}^2$) to conduct the most accurate measurement to date of the power spectrum of fluctuations of the unresolved CXB on the angular scales of $\sim 3$arcsec $-$ $\sim 17$arcmin. We find that at sub-arcmin angular scales, the power spectrum is consistent with the AGN shot noise, without much need for any significant contribution from their one-halo term. This is consistent with the theoretical expectation that low-luminosity AGN reside alone in their dark matter halos. However, at larger angular scales we detect a significant LSS signal above the AGN shot noise. Its power spectrum, obtained after subtracting the AGN shot noise, follows a power law with the slope of $-0.8\pm 0.1$ and its amplitude is much larger than what can be plausibly explained by the two-halo term of AGN. We demonstrate that the detected LSS signal is produced by unresolved clusters and groups of galaxies. For the flux limit of the XBOOTES survey, their flux-weighted mean redshift equals $⟨z⟩\sim 0.3$, and the mean temperature of their intracluster medium (ICM), $⟨T⟩\approx 1.4$ keV, corresponds to the mass of $M_{500}\sim 10^{13.5}{\mathrm{M}}_{\odot }$. The power spectrum of CXB fluctuations carries information about the redshift distribution of these objects and the spatial structure of their ICM on the linear scales of up to $\sim$Mpc, i.e. of the order of the virial radius.

25 pages, 20 figures, submitted to MNRAS, comments welcome

References in corpus (18)

• The synthesis of the cosmic X-ray background in the Chandra and XMM-Newton era
• Toward the Standard Population Synthesis Model of the X-Ray Background: Evolution of X-Ray Luminosity and Absorption Functions of Active Galactic Nuclei Including Compton-Thick Populations
• The XMM-Newton wide-field survey in the COSMOS field: VI. Statistical properties of clusters of galaxies
• Unifying X-ray Scaling Relations from Galaxies to Clusters
• A new method for determining the sensitivity of X-ray imaging observations and the X-ray number counts
• Correlation between the photon index and X-ray luminosity of black hole X-ray binaries and active galactic nuclei: observations and interpretation
• Chandra Multiwavelength Project X-ray Point Source Number Counts and the Cosmic X-ray Background
• Detailed Shape and Evolutionary Behavior of the X-ray Luminosity Function of Active Galactic Nuclei
• High redshift quasars in the COSMOS survey: the space density of z>3 X-ray selected QSOs
• The extended ROSAT-ESO Flux Limited X-ray Galaxy Cluster Survey (REFLEX II) IV. X-ray Luminosity Function and First Constraints on Cosmological Parameters
• The Spatial Clustering of ROSAT All-Sky Survey AGN: I. The cross-correlation function with SDSS Luminous Red Galaxies
• Clustering properties of moderate luminosity X-ray selected Type 1 and Type 2 AGN at z~3
• The nature of the unresolved extragalactic soft CXB
• The Sunyaev-Zel'dovich effects from a cosmological hydrodynamical simulation: large-scale properties and correlation with the soft X-ray signal
• The Quiescent X-ray Spectrum of Accreting Black Holes
• The Dark Matter Halos of Moderate Luminosity X-ray AGN as Determined from Weak Gravitational Lensing and Host Stellar Masses
• Ultra-deep catalog of X-ray groups in the Extended Chandra Deep Field South
• X-ray and Sunyaev-Zeldovich properties of the WHIM

Cited by in corpus (2)

• Probing large scale coherence between Spitzer IR and Chandra X-ray source-subtracted cosmic backgrounds
• Studying the ICM in clusters of galaxies via surface brightness fluctuations of the cosmic X-ray background