Decrease in the Brightness of the Cosmic X-ray and Soft Gamma-ray Background toward Clusters of Galaxies

Abstract

We show that Compton scattering by electrons of the hot intergalactic gas in galaxy clusters should lead to peculiar distortions of the cosmic background X-ray and soft gamma-ray radiation - an increase in its brightness at E<60-100 keV and a drop at higher energies. The distortions allow the most important cluster parameters to be measured. The spectral shape of the distortions and its dependence on the gas temperature, optical depth, and surface density distribution law have been studied using Monte Carlo computations and confirmed by analytical estimations. In the cluster frame the maximum of the background decrease due to the recoil effect occurs at ~500-600 keV. The photoionization of H- and He-like iron and nickel ions leads to additional distortions in the background spectrum - a strong absorption line with the threshold at ~9 keV (and also to an absorption jump at ~2 keV for cold clusters). The absorption of intrinsic thermal radiation from the cluster gas by these ions also leads to such lines. In nearby (z<1) clusters the line at ~2 keV is noticeably enhanced by absorption in the colder (~10^6 K) plasma of their peripheral (~3 Mpc) regions; moreover, the absorption line at ~1.3 keV splits off from it. The redshift of distant clusters shifts the absorption lines in the background spectrum (at ~2, ~9, and ~500 keV) to lower energies. Thus, in contrast to the microwave background scattering effect, this effect depends on the cluster redshift z, but in a very peculiar way. When observing clusters at z>1, the effect allows one to determine how the X-ray background evolved and how it was "gathered" with z. To detect the effect, the accuracy of measurements should reach ~0.1%. We consider the most promising clusters for observing the effect and discuss the techniques whereby the influence of the thermal gas radiation hindering the detection of background distortions should be minimal.

25 pages, 15 figures, 4 tables

References in corpus (40)

• A Universal Density Profile from Hierarchical Clustering
• The Nuclear Spectroscopic Telescope Array (NuSTAR) Mission
• Atomic Data for Astrophysics. II. New Analytic Fits for Photoionization Cross Sections of Atoms and Ions
• Chandra sample of nearby relaxed galaxy clusters: mass, gas fraction, and mass-temperature relation
• The Cosmic Baryon Budget
• Where are the Baryons?
• Cosmology with the Sunyaev-Zel'dovich Effect
• The universal galaxy cluster pressure profile from a representative sample of nearby systems (REXCESS) and the Y_SZ-M_500 relation
• The Sunyaev-Zel'dovich Effect
• Galaxy Clusters Discovered via the Sunyaev-Zel'dovich Effect in the 2500-square-degree SPT-SZ survey
• 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
• A Textbook Example of a Bow Shock in the Merging Galaxy Cluster 1E0657-56
• Planck 2013 results. XXIX. Planck catalogue of Sunyaev-Zeldovich sources
• First Results from the X-ray and Optical Survey of the Chandra Deep Field South
• A New Robust Low-Scatter X-ray Mass Indicator for Clusters of Galaxies
• The Lyman Alpha Forest in the Spectra of QSOs
• An investigation of cooling flows and general cluster properties from an X-ray image deprojection analysis of 207 clusters of galaxies
• The Atacama Cosmology Telescope: Sunyaev-Zel'dovich Selected Galaxy Clusters at 148 GHz from Three Seasons of Data
• The Spectrum of Diffuse Cosmic Hard X-Rays Measured with HEAO-1
• A correlation of the cosmic microwave sky with large scale structure
• An SZ-selected sample of the most massive galaxy clusters in the 2500-square-degree South Pole Telescope survey
• INTEGRAL observations of the cosmic X-ray background in the 5-100 keV range via occultation by the Earth
• The Atacama Cosmology Telescope: ACT-CL J0102-4915 "El Gordo," a Massive Merging Cluster at Redshift 0.87
• X-ray Properties of SPT Selected Galaxy Clusters at 0.2<z<1.5 Observed with XMM-Newton
• Planck 2013 results. XXIX. The Planck catalogue of Sunyaev-Zeldovich sources: Addendum
• Detailed Shape and Evolutionary Behavior of the X-ray Luminosity Function of Active Galactic Nuclei
• XMM-Newton discovery of an X-ray filament in Coma
• A weak lensing study of the Coma cluster
• Planck Early Results XXVI: Detection with Planck and confirmation by XMM-Newton of PLCK G266.6-27.3, an exceptionally X-ray luminous and massive galaxy cluster at z~1
• Deep Chandra, HST-COS, and Megacam Observations of the Phoenix Cluster: Extreme Star Formation and AGN Feedback on Hundred Kiloparsec Scales
• Analytical model for non-thermal pressure in galaxy clusters - III. Removing the hydrostatic mass bias
• Analytical model for non-thermal pressure in galaxy clusters
• The profile of a narrow line after single scattering by Maxwellian electrons: relativistic corrections to the kernel of the integral kinetic equation
• Compton Heating of the Intergalactic Medium by the Hard X-ray Background
• Cumulative hard X-ray spectrum of local AGN: a link to the cosmic X-ray background
• Planck intermediate results. XL. The Sunyaev-Zeldovich signal from the Virgo cluster
• Investigating the origins of the CMB-XRB cross correlation
• Resonant scattering of X-rays by the warm intergalactic medium
• Large Scale Fluctuations in the X-Ray Background
• Constraining the past X-ray luminosity of AGN in clusters of galaxies: the role of resonant scattering

Cited by in corpus (4)

• NuSTAR measurement of the cosmic X-ray background in the 3-20 keV energy band
• Refined modelling of the radio SZ signal: kinematic terms, relativistic temperature corrections and anisotropies in the radio background
• Increase in the Brightness of the Cosmic Radio Background toward Galaxy Clusters
• X-ray and Gamma-ray Emission from a High-Temperature Plasma and the Spectra of Accreting Black Holes