A compact symmetric radio source born at one-tenth the current age of the Universe

An, Tao; Wang, Ailing; Zhang, Yingkang; Aditya, J. N. H. S.; Hong, Xiaoyu; Cui, Lang

doi:10.1093/mnras/stac205

Cited by 12 publications

(17 citation statements)

References 75 publications

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“…This value is consistent to what is normally found in other RL QSOs at similar frequencies (e.g., Bruni et al 2012), even when considering the few at z > 6 (Frey et al 2011;Bañados et al 2021). However, the nondetection at 9 GHz might imply a steepening of the spectrum at higher frequencies, again, in a similar way to what has been observed in other high-redshift radio sources (e.g., Drouart et al 2020;An et al 2022).…”

Section: Radio Spectrumsupporting

confidence: 90%

Constraining the radio properties of the z = 6.44 QSO VIK J2318−3113

Ighina

Leung

Broderick

et al. 2022

A&A

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The recent detection of the quasi-stellar object (QSO) VIKING J231818.3−311346 (hereafter VIK J2318−3113) at redshift z = 6.44 in the Rapid ASKAP Continuum Survey (RACS) uncovered its radio-loud nature, making it one of the most distant known to date in this class. By using data from several radio surveys of the Galaxy And Mass Assembly 23h field and from a dedicated follow-up, we were able to constrain the radio spectrum of VIK J2318−3113 in the observed range ∼0.1–10 GHz. At high frequencies (0.888–5.5 GHz in the observed frame) the QSO presents a steep spectrum (αr = 1.24, with Sν ∝ ν−αr), while at lower frequencies (0.4–0.888 GHz in the observed frame) it is nearly flat. The overall spectrum can be modelled by either a curved function with a rest-frame turnover around 5 GHz, or with a smoothly varying double power law that is flat below a rest-frame break frequency of about 20 GHz and above which it significantly steepens. Based on the model adopted, we estimated that the radio jets of VIK J2318−3113 must be a few hundred years old in the case of a turnover, or less than a few × 104 years in the case of a break in the spectrum. Having multiple observations at two frequencies (888 MHz and 5.5 GHz), we further investigated the radio variability previously reported for this source. We found that the marginally significant flux density variations are consistent with the expectations from refractive interstellar scintillation, even though relativistic effects related to the orientation of the source may still play a non-negligible role. Further radio and X-ray observations are required to conclusively discern the nature of this variation.

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Section: Radio Spectrumsupporting

confidence: 90%

Constraining the radio properties of the z = 6.44 QSO VIK J2318−3113

Ighina

Leung

Broderick

et al. 2022

A&A

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show abstract

“…However, the non-detection at 9 GHz might imply a steepening of the spectrum at higher frequencies, again, in a similar way to what has been observed in other high-redshift radio sources (e.g. Drouart et al 2020;An et al 2022).…”

Section: Radio Spectrumsupporting

confidence: 73%

Constraining the Radio Properties of the $z$=6.44 QSO VIK J2318$-$3113

Ighina,

Leung,

Broderick

et al. 2022

Preprint

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The recent detection of the quasi-stellar object (QSO) VIKING J231818.3−311346 (hereafter VIK J2318−3113) at redshift z = 6.44 in the Rapid ASKAP Continuum Survey (RACS) uncovered its radio-loud nature, making it one of the most distant known to date in this class. By using data from several radio surveys of the Galaxy and Mass Assembly 23 h field and from dedicated follow-up, we were able to constrain the radio spectrum of VIK J2318−3113 in the observed range ∼0.1-10 GHz. At high frequencies (0.888-5.5 GHz in the observed frame) the QSO presents a steep spectrum (α r =1.24, with S ν ∝ ν −αr ), while at lower frequencies (0.4-0.888 GHz in the observed frame) it is nearly flat. The overall spectrum can be modelled by either a curved function with a rest-frame turnover around 5 GHz, or with a smoothly varying double power law that is flat below a rest-frame break frequency of about 20 GHz and which significantly steepens above it. Based on the model adopted, we estimated that the radio jets of VIK J2318−3113 must be a few hundred years old, in the case of a turnover, or less than few×10 4 years, in the case of a break in the spectrum. Having multiple observations at two frequencies (888 MHz and 5.5 GHz), we further investigated the radio variability previously reported for this source. We found that the marginally significant flux density variations are consistent with the expectations from refractive interstellar scintillation, even though relativistic effects related to the orientation of the source may still play a non-negligible role. Further radio and X-ray observations are required to conclusively discern the nature of this variation.

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“…Therefore, we suggest that J1520+1835 is a CSO candidate. The number of high-redshift CSOs (and candidates) observed so far is extremely small (Frey et al 2008;An et al 2022). Although limited observational data are available on this source, we note that, qualitatively, the suspected morphology on the angular scale of tens of mas described above makes it similar to the low-redshift CSO quasar PKS 1117+146 (Bondi et al 1998).…”

Section: Classification and Notes On Individual Sourcesmentioning

confidence: 64%

Radio-loud Quasars above Redshift 4: Very Long Baseline Interferometry (VLBI) Imaging of an Extended Sample

Krezinger

Perger

Gabányi

et al. 2022

ApJS

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High-redshift radio sources provide plentiful opportunities for studying the formation and evolution of early galaxies and supermassive black holes. However, the number of known radio-loud active galactic nuclei (AGN) above redshift 4 is rather limited. At high redshifts, it appears that blazars, with relativistically beamed jets pointing toward the observer, are in the majority compared to the radio-loud sources with jets misaligned with respect to the line of sight. To find more of these misaligned AGN, milliarcsecond-scale imaging studies carried out with very long baseline interferometry (VLBI) are needed, as they allow us to distinguish between compact-core–jet radio sources and those with more extended emission. Previous high-resolution VLBI studies revealed that some of the radio sources among blazar candidates in fact show unbeamed radio emission on milliarcsecond scales. The most accurate optical coordinates determined with the Gaia astrometric space mission are also useful in the classification process. Here, we report on dual-frequency imaging observations of 13 high-redshift (4 < z < 4.5) quasars at 1.7 and 5 GHz with the European VLBI Network. This sample increases the number of z > 4 radio sources for which VLBI observations are available by about a quarter. Using structural and physical properties, such as radio morphology, spectral index, variability, brightness temperature, as well as optical coordinates, we identified six blazars and six misaligned radio AGNs, with the remaining one tentatively identified as blazar.

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A compact symmetric radio source born at one-tenth the current age of the Universe

Cited by 12 publications

References 75 publications

Constraining the radio properties of the z = 6.44 QSO VIK J2318−3113

Constraining the radio properties of the z = 6.44 QSO VIK J2318−3113

Constraining the Radio Properties of the $z$=6.44 QSO VIK J2318$-$3113

Radio-loud Quasars above Redshift 4: Very Long Baseline Interferometry (VLBI) Imaging of an Extended Sample

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