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Please use this identifier to cite or link to this item: http://hdl.handle.net/20.500.12386/26880
Title: CMB-induced radio quenching of high-redshift jetted AGNs with highly magnetic hotspots
Authors: Wu, Jianfeng
GHISELLINI, Gabriele 
Hodges-Kluck, Edmund
Gallo, Elena
Ciardi, Benedetta
HAARDT, FRANCESCO
Sbarrato, Tullia 
TAVECCHIO, Fabrizio 
Issue Date: 2017
Journal: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 
Number: 468
Issue: 1
First Page: 109
Abstract: In an effort to understand the cause of the apparent depletion in the number density of radio-loud active galactic nuclei (AGNs) at z > 3, this work investigates the viability of the so-called cosmic microwave background (CMB) quenching mechanism of intrinsically jetted, high-z AGNs, whereby inverse Compton scattering of CMB photons off electrons within the extended lobes results in a substantial dimming of the lobe synchrotron emission at GHz frequencies, while simultaneously boosting their diffuse X-ray signal. We focus on five z > 3.5 radio galaxies that have sufficiently deep Chandra exposure (>50 ks) to warrant a meaningful investigation of any extended X-ray emission. For those objects with evidence for statistically significant extended X-ray lobes (4C 41.17 and 4C 03.24), we combine the Chandra measurements with literature data at lower frequencies to assemble the systems' spectral energy distributions (SEDs), and utilize state-of-the-art SED modelling - including emission from the disc, torus, jet, hotspots and lobes - to infer their physical parameters. For both radio galaxies, the magnetic energy density in the hotspots is found to exceed the energy density in CMB photons, whereas the opposite is true for the lobes. This implies that any extended synchrotron emission likely originates from the hotspots themselves, rather than the lobes. Conversely, inverse Compton scattering of CMB photons dominates the extended X-ray emission from the lobes, which are effectively 'radio-quenched'. As a result, CMB quenching is effective in these systems in spite of the fact that the observed X-ray to radio luminosity ratio does not bear the signature (1 + z)<SUP>4</SUP> dependence of the CMB energy density.
URI: http://hdl.handle.net/20.500.12386/26880
URL: https://academic.oup.com/mnras/article/468/1/109/3038247
ISSN: 0035-8711
DOI: 10.1093/mnras/stx416
Bibcode ADS: 2017MNRAS.468..109W
Fulltext: open
Appears in Collections:1.01 Articoli in rivista

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