X-ray properties of z &amp;gt; 4 blazars

Ighina, L.; Caccianiga, A.; Moretti, A.; Belladitta, S.; Ceca, R. Della; Ballo, L.; Dallacasa, D.

doi:10.1093/mnras/stz2340

“…[33]). Moreover, the powerful aligned jets are not affected by the obscuring torus that surrounds the central black hole and have more chances to break through the surrounding material [34], making the high-z sources prominent in multi-band studies [35,36]. Apparent proper motion estimates of AGN jets provide a unique way of understanding their relativistic motions.…”

Section: Discussionmentioning

confidence: 99%

Fast jet proper motion discovered in a blazar at z=4.72

Zhang

¹

,

An

²

,

Frey

³

2020

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High-resolution observations of high-redshift (z > 4) radio quasars offer a unique insight into jet kinematics at early cosmological epochs, as well as constraints on cosmological model parameters. Due to the general weakness of extremely distant objects and the apparently slow structural changes caused by cosmological time dilation, only a couple of high-redshift quasars have been studied with parsec-scale resolutions, and with limited number of observing epochs. Here we report on very long baseline interferometry (VLBI) observations of a high-redshift blazar J1430+4204 (z = 4.72) in the 8 GHz frequency band at five different epochs spanning 22 years. The source shows a compact core-jet structure with two jet components being identified within 3 milli-arcsecond (mas) scale. The long time span and multiple-epoch data allow for the kinematic studies of the jet components. That results in a jet proper motion of µ(J1) = 0.017±0.002 mas yr −1 and µ(J2)=0.156±0.015 mas yr −1 , respectively. For the fastestmoving outer jet component J2, the corresponding apparent transverse speed is 19.5 ± 1.9 c. The inferred bulk jet Lorentz factor Γ = 14.6 ± 3.8 and viewing angle θ = 2.2 • ± 1.6 • indicate highly relativistic beaming. The Lorentz factor and apparent proper motion are the highest measured to date among the z > 4 jetted radio sources, while the jet kinematics is still consistent with the cosmological interpretation of quasar redshifts.

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“…following Ighina et al 2019). Miller et al (2011) argued that the lack of redshift evolution seen in Δα OX for radio-loud quasars was indicative that IC/CMB only produced, at most, a minor contribution to the X-ray emission from these quasars.…”

Section: X-ray Loudnessmentioning

confidence: 99%

Enhanced X-Ray Emission from the Most Radio-powerful Quasar in the Universe’s First Billion Years

Connor

¹

,

Bañados

²

,

Stern

³

et al. 2021

ApJ

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We present deep (265 ks) Chandra X-ray observations of PSO J352.4034−15.3373, a quasar at z = 5.831 that, with a radio-to-optical flux ratio of R > 1000, is one of the radio-loudest quasars in the early universe and is the only quasar with observed extended radio jets of kiloparsec scale at z ≳ 6. Modeling the X-ray spectrum of the quasar with a power law, we find a best fit of Γ = 1.99 − 0.28 + 0.29 , leading to an X-ray luminosity of L 2 – 10 = 1.26 − 0.33 + 0.45 × 10 45 erg s − 1 and an X-ray to UV brightness ratio of α OX = −1.45 ± −0.11. We identify a diffuse structure 50 kpc (∼8″) to the NW of the quasar along the jet axis that corresponds to a 3σ enhancement in the angular density of emission and can be ruled out as a background fluctuation with a probability of P = 0.9985. While with few detected photons the spectral fit of the structure is uncertain, we find that it has a luminosity of L 2–10 ∼ 1044 erg s−1. These observations therefore potentially represent the most distant quasar jet yet seen in X-rays. We find no evidence for excess X-ray emission where the previously reported radio jets are seen (which have an overall linear extent of 0.″28), and a bright X-ray point source located along the jet axis to the SE is revealed by optical and NIR imaging to not be associated with the quasar.

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“…We reviewed literature that studied large numbers of blazars (e.g. Perlman et al 1998;Donato, Sambruna & Gliozzi 2005;Eitan & Behar 2013;Ighina et al 2019;Marcotulli et al 2020) and, within our criteria, selected objects randomly for our sample. Our sample has 14 with z > 2, a high fraction of the total available as noted above.…”

Section: Data S E L E C T I O N a N D M E T H O D O L O G Ymentioning

confidence: 99%

Probing the physical properties of the intergalactic medium using blazars

Dalton

¹

,

Morris

²

,

Fumagalli

³

et al. 2021

Monthly Notices of the Royal Astronomical Society

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We use Swift blazar spectra to estimate the key intergalactic medium (IGM) properties of hydrogen column density (${N} {\rm \small {HXIGM}}$), metallicity and temperature over a redshift range of 0.03 ≤ z ≤ 4.7, using a collisional ionisation equilibrium (CIE) model for the ionised plasma. We adopted a conservative approach to the blazar continuum model given its intrinsic variability and use a range of power law models. We subjected our results to a number of tests and found that the ${N}{\rm \small {hxigm}}$ parameter was robust with respect to individual exposure data and co-added spectra for each source, and between Swift and XMM-Newton source data. We also found no relation between ${N}{\rm \small {hxigm}}$ and variations in source flux or intrinsic power laws. Though some objects may have a bulk Comptonisation component which could mimic absorption, it did not alter our overall results. The ${N}{\rm \small {hxigm}}$ from the combined blazar sample scales as (1 + z)1.8 ± 0.2. The mean hydrogen density at z = 0 is n0 = (3.2 ± 0.5) × 10−7 cm−3. The mean IGM temperature over the full redshift range is log(T/K) =6.1 ± 0.1, and the mean metallicity is [X/H] = −1.62 ± 0.04(Z ∼ 0.02). When combining with the results with a gamma-ray burst (GRB) sample, we find the results are consistent over an extended redshift range of 0.03 ≤ z ≤ 6.3. Using our model for blazars and GRBs, we conclude that the IGM contributes substantially to the total absorption seen in both blazar and GRB spectra.

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X-ray properties of z > 4 blazars

Cited by 35 publications

References 58 publications

Fast jet proper motion discovered in a blazar at z=4.72

Fast jet proper motion discovered in a blazar at z=4.72

Enhanced X-Ray Emission from the Most Radio-powerful Quasar in the Universe’s First Billion Years

Probing the physical properties of the intergalactic medium using blazars

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