X-ray absorption towards high-redshift sources: probing the intergalactic medium with blazars

Abstract

The role played by the intergalactic medium (IGM) in the X-ray absorption towards high-redshift sources has recently drawn more attention in spectral analysis studies. Here, we study the X-ray absorption towards 15 flat-spectrum radio quasars at $z>2$, relying on high counting statistic ($\gtrsim 10000$ photons) provided by XMM-Newton, with additional NuSTAR (and simultaneous Swift-XRT) observations when available. Blazars can be confidently considered to have negligible X-ray absorption along the line of sight within the host galaxy, likely swept by the kpc-scale relativistic jet. This makes our sources ideal for testing the absorption component along the IGM. Our new approach is to revisit the origin of the soft X-ray spectral hardening observed in high-z blazars in terms of X-ray absorption occurring along the IGM, with the help of a low-z sample used as comparison. We verify that the presence of absorption in excess of the Galactic value is the preferred explanation to explain the observed hardening, while intrinsic energy breaks, predicted by blazars' emission models, can easily occur out of the observing energy band in most sources. First, we perform an indirect analysis comparing the inferred amount of absorption in excess of the Galactic value with a simulated IGM absorption contribution, that increases with redshift and includes both a minimum component from diffuse IGM metals, and the additional contribution of discrete denser intervening regions. Then, we directly investigate the warm-hot IGM with a spectral model on the best candidates of our sample, obtaining an average IGM density of $n_0=1.01_{-0.72}^{+0.53}\times 10^{-7}$ cm${}^{-3}$ and temperature of $\log (T/\text{K})=6.45_{-2.12}^{+0.51}$. A more dedicated study is currently beyond reach, but our results can be used as a stepping stone for future more accurate analysis, involving Athena.

32 pages, 7 figures. Accepted, to be published in A&A

References in corpus (32)

• The Supernova -- Gamma-Ray Burst Connection
• Long gamma-ray bursts and core-collapse supernovae have different environments
• Active Galactic Nuclei: what's in a name?
• BAT AGN Spectroscopic Survey - V. X-ray properties of the Swift/BAT 70-month AGN catalog
• Kinematics of Parsec-Scale Jets of Gamma-Ray Blazars at 43~GHz within the VLBA-BU-BLAZAR Program
• The Search for the Missing Baryons at Low Redshift
• Observations of the MIssing Baryons in the warm-hot intergalactic medium
• The Hard X-ray Spectrum as a Probe for Black-Hole Growth in Radio-Quiet Active Galactic Nuclei
• The Hard X-ray Spectral Slope as an Accretion-Rate Indicator in Radio-Quiet Active Galactic Nuclei
• The faint radio sky: radio astronomy becomes mainstream
• Fermi/LAT broad emission line blazars
• The spectrum of the Broad Line Region and the high-energy emission of powerful blazars
• On the two main classes of Active Galactic Nuclei
• IACHEC Cross-Calibration of Chandra, NuSTAR, Swift, Suzaku, and XMM-Newton with 3C 273 and PKS 2155-304
• Very different X-ray to optical column density ratios in gamma-ray burst afterglows: ionisation in GRB environments
• MOJAVE XII: Acceleration and Collimation of Blazar Jets on Parsec Scales
• The X-ray properties of z$\sim$6 luminous quasars
• A Multi-epoch VLBI Survey of the Kinematics of Caltech-Jodrell Bank Flat-Spectrum Sources, Part II: Analysis of the Kinematics
• The Cosmic Evolution of the Metallicity Distribution of Ionized Gas Traced by Lyman Limit Systems
• Bulk Comptonization spectra in blazars
• Blazar candidates beyond redshift 4 observed by Swift
• Low energy cut-offs and hard X-ray spectra in high-z radio-loud quasars: the Suzaku view of RBS315
• XMM-Newton observations of a sample of gamma-ray loud active galactic nuclei
• Swift observations of high-redshift radio-loud quasars
• Missing cosmic metals revealed by X-ray absorption towards distant sources
• X-ray emission from the blazar AO 0235+16: the XMM-Newton and Chandra point of view
• NuSTAR and multifrequency study of the two high-redshift blazars S5 0836+710 and PKS 2149-306
• X-ray spectral properties of high-redshift radio-loud quasars beyond redshift 4--first results
• The High Redshift Blazar S5 0836+71: A Broadband Study
• Signature of Inverse Compton emission from blazars
• Radio and X-ray observations of an exceptional radio flare in the extreme z=4.72 blazar GB B1428+4217
• Effective absorbing column density in the gamma-ray burst afterglow X-ray spectra

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