New Radio-Loud QSOs at the end of the Re-ionisation Epoch

Abstract

We present the selection of high-redshift ($z\gtrsim 5.7$) radio-loud (RL) quasi-stellar object (QSO) candidates from the combination of the radio Rapid ASKAP Continuum Survey (RACS; at 888 MHz) and the optical/near-infrared Dark Energy Survey (DES). In particular, we selected six candidates brighter than $S_{888MHz}>1$ mJy beam${}^{-1}$ and $\mathrm{mag}(z_{\mathrm{DES}})<21.3$ using the dropout technique (in the $i$-band). From this sample, we were able to confirm the high-$z$ nature ($z\sim 6.1$) of two sources, which are now among the highest-redshift RL QSOs currently known. Based on our Gemini-South/GMOS observations, neither object shows a prominent Ly$\alpha$ emission line. This suggests that both sources are likely to be weak emission-line QSOs hosting radio jets and would therefore further strengthen the potential increase of the fraction of weak emission-line QSOs recently found in the literature. However, further multiwavelength observations are needed to constrain the properties of these QSOs and of their relativistic jets. From the discovery of these two sources, we estimated the space density of RL QSOs in the redshift range $5.9<z<6.4$ to be 0.13${}_{-0.09}^{+0.18}$ and found it to be consistent with the expectations based on our current knowledge of the blazar population up to $z\sim 5$.

Accepted in MNRAS on 05 December 2022. Ten pages with five figures and three tables

References in corpus (44)

• Cosmology at Low Frequencies: The 21 cm Transition and the High-Redshift Universe
• The LOFAR Two-metre Sky Survey - I. Survey Description and Preliminary Data Release
• The LOFAR Two-metre Sky Survey -- V. Second data release
• A Luminous Quasar at Redshift 7.642
• The Pan-STARRS1 distant z>5.6 quasar survey: more than 100 quasars within the first Gyr of the universe
• Pōniuā'ena: A Luminous $z=7.5$ Quasar Hosting a 1.5 Billion Solar Mass Black Hole
• The Final SDSS High-Redshift Quasar Sample of 52 Quasars at z>5.7
• Physical properties of 15 quasars at $z\gtrsim 6.5$
• Australian Square Kilometre Array Pathfinder: I. System Description
• The Rapid ASKAP Continuum Survey I: Design and First Results
• Radio galaxies and feedback from AGN jets
• A Quick Look at the $3$GHz Radio Sky I. Source Statistics from the Very Large Array Sky Survey
• Relativistic Beaming and the Intrinsic Properties of Extragalactic Radio Jets
• The Rapid ASKAP Continuum Survey Paper II: First Stokes I Source Catalogue Data Release
• X-ray Insights into the Nature of PHL 1811 Analogs and Weak Emission-Line Quasars: Unification with a Geometrically Thick Accretion Disk?
• Kiloparsec-scale ALMA Imaging of [CII] and Dust Continuum Emission of 27 Quasar Host Galaxies at z~6
• Discovery of eight z ~ 6 quasars from Pan-STARRS1
• On the two main classes of Active Galactic Nuclei
• Constraining the radio-loud fraction of quasars at z>5.5
• Three new VHS-DES Quasars at 6.7 < z < 6.9 and Emission Line Properties at z > 6.5
• The first blazar observed at z>6
• Two bright z > 6 quasars from VST ATLAS and a new method of optical plus mid-infra-red colour selection
• The discovery of a highly accreting, radio-loud quasar at z=6.82
• Molecular gas in z~6 quasar host galaxies
• Constraining the quasar radio-loud fraction at $z\sim 6$ with deep radio observations
• Parsec-scale properties of the radio brightest jetted AGN at z > 6
• Probing the Nature of High Redshift Weak Emission Line Quasars: A Young Quasar with a Starburst Host Galaxy
• The primordial environment of supermassive black holes (II): deep Y and J band images around the z=6.3 quasar SDSS J1030+0524
• A large sample of Kohonen-selected SDSS quasars with weak emission lines: selection effects and statistical properties
• The space density of z>4 blazars
• Radio Detection of VIK J2318$-$3113, the Most Distant Radio-Loud Quasar ($z$=6.44)
• Radio and Far-IR Emission Associated with a Massive Star-forming Galaxy Candidate at z$\simeq$6.8: A Radio-Loud AGN in the Reionization Era?
• A search for faint high-redshift radio galaxy candidates at 150 MHz
• The evolution of the heaviest super-massive black-holes in jetted AGNs
• Direct observation of an extended X-ray jet at $z$=6.1
• Measuring the Density Fields around Bright Quasars at $z\sim 6$ with XQR-30 Spectra
• The radio spectral turnover of radio-loud quasars at $z>5$
• The central engine of the highest redshift blazar
• The GLEAMing of the First Supermassive Black Holes
• Conditions for direct black hole seed collapse near a radio-loud quasar 1 Gyr after the Big Bang
• Constraining the Radio Properties of the $z$=6.44 QSO VIK J2318$-$3113
• Predictions for the 21cm-galaxy cross-power spectrum observable with SKA and future galaxy surveys
• GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey III: South Galactic Pole data release
• The Infrared Medium-deep Survey. IX. Discovery of Two New $z\sim 6$ Quasars and Space Density down to $M_{1450}\sim -23.5$ mag

Cited by in corpus (13)

• The SRG/eROSITA All-Sky Survey: X-ray beacons at late cosmic dawn
• A powerful (and likely young) radio-loud quasar at z=5.3
• The extremely X-ray luminous radio-loud quasar CFHQS J142952+544717 at $z=6.18$ under Chandra high-angular resolution lens
• Discovery and characterization of 25 new quasars at 4.6 < z < 6.9 from wide-field multi-band surveys
• Prospects for Observing High-redshift Radio-loud Quasars in the SKA Era: Paving the Way for 21-cm Forest Observations
• Multi-wavelength properties of three new radio-powerful $z\sim 5.6$ quasi-stellar objects discovered from RACS
• Comprehensive view on a $z\sim 6.5$ radio-loud QSO: from the radio to the optical/NIR to the X-ray band
• High-$z$ radio Quasars in RACS I: Selection, identification, and multi-wavelength properties
• Prospects of a statistical detection of the 21-cm forest and its potential to constrain the thermal state of the neutral IGM during reionization
• Prospects for measuring neutrino mass with 21-cm forest
• Radio and Optical Properties of the blazar PKS 1614+051 at z=3.21
• Milliarcsecond-scale radio structure of the most distant BL Lac object candidate at redshift 6.57
• 4MOST ChANGES: Catalog of high-redshift quasar candidates (4.5 < $z$ < 7) selected with SED fitting