Constraining the radio-loud fraction of quasars at z>5.5

Abstract

Radio-loud Active Galactic Nuclei at z~2-4 are typically located in dense environments and their host galaxies are among the most massive systems at those redshifts, providing key insights for galaxy evolution. Finding radio-loud quasars at the highest accessible redshifts (z~6) is important to study their properties and environments at even earlier cosmic time. They would also serve as background sources for radio surveys intended to study the intergalactic medium beyond the epoch of reionization in HI 21 cm absorption. Currently, only five radio-loud ($R=f_{\nu ,5\mathrm{GHz}}/f_{\nu ,4400\mathring{A}}>10$) quasars are known at z~6. In this paper we search for 5.5 < z < 7.2 quasars by cross-matching the optical Pan-STARRS1 and radio FIRST surveys. The radio information allows identification of quasars missed by typical color-based selections. While we find no good 6.4 < z <7.2 quasar candidates at the sensitivities of these surveys, we discover two new radio-loud quasars at z~6. Furthermore, we identify two additional z~6 radio-loud quasars which were not previously known to be radio-loud, nearly doubling the current z~6 sample. We show the importance of having infrared photometry for z>5.5 quasars to robustly classify them as radio-quiet or radio-loud. Based on this, we reclassify the quasar J0203+0012 (z=5.72), previously considered radio-loud, to be radio-quiet. Using the available data in the literature, we constrain the radio-loud fraction of quasars at z~6, using the Kaplan--Meier estimator, to be $8.1_{-3.2}^{+5.0}\%$. This result is consistent with there being no evolution of the radio-loud fraction with redshift, in contrast to what has been suggested by some studies at lower redshifts.

Accepted for publication in ApJ. 3 Figures. 3 Tables

References in corpus (24)

• A luminous quasar at a redshift of z = 7.085
• Cosmology at Low Frequencies: The 21 cm Transition and the High-Redshift Universe
• Observational constraints on Cosmic Reionization
• The Sloan Digital Sky Survey Quasar Catalog IV. Fifth Data Release
• Evidence of patchy hydrogen reionization from an extreme Ly$\alpha$ trough below redshift six
• GROND - a 7-channel imager
• Four quasars above redshift 6 discovered by the Canada-France High-z Quasar Survey
• The Radio-Loud Fraction of Quasars is a Strong Function of Redshift and Optical Luminosity
• Black hole masses and enrichment of z ~ 6 SDSS quasars
• Protoclusters associated with z > 2 radio galaxies. I. Characteristics of high redshift protoclusters
• A Survey of z~6 Quasars in the SDSS Deep Stripe: I. a Flux-Limited Sample at z_{AB}<21
• The identification of z-dropouts in Pan-STARRS1: three quasars at 6.5<z<6.7
• Thermal Emission from Warm Dust in the Most Distant Quasars
• Discovery of eight z ~ 6 quasars from Pan-STARRS1
• Six more quasars at redshift 6 discovered by the Canada-France High-z Quasar Survey
• Why z > 1 radio-loud galaxies are commonly located in proto-clusters
• High-resolution VLA Imaging of SDSS Stripe 82 at 1.4 GHz
• Millimeter and Radio Observations of z~6 Quasars
• The Discovery of Three New z>5 Quasars in the AGN and Galaxy Evolution Survey
• High-resolution double morphology of the most distant known radio quasar at z=6.12
• High-resolution radio imaging of the most distant radio quasar SDSS J0836+0054
• The spectral energy distribution of the redshift 7.1 quasar ULAS J1120+0641
• A Sample of Candidate Radio Stars in FIRST and SDSS
• M dwarfs in the b201 tile of the VVV survey: Colour-based Selection, Spectral Types and Light Curves

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• Copious Amounts of Dust and Gas in a z=7.5 Quasar Host Galaxy
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• The discovery of a highly accreting, radio-loud quasar at z=6.82
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• The Pan-STARRS1 z>5.6 quasar survey II: Discovery of 55 Quasars at 5.6<z<6.5
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• Discovery of 24 radio-bright quasars at $4.9\le z\le 6.6$ using low-frequency radio observations
• First constraints on the AGN X-ray luminosity function at $z\sim 6$ from an eROSITA-detected quasar
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• Radio Detection of VIK J2318$-$3113, the Most Distant Radio-Loud Quasar ($z$=6.44)
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• 21 cm Forest Constraints on Primordial Black Holes
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• Blazar nature of high-z radio-loud quasars
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• Proof of CMB-driven X-ray brightening of high-z radio galaxies
• A powerful (and likely young) radio-loud quasar at z=5.3
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• The extremely X-ray luminous radio-loud quasar CFHQS J142952+544717 at $z=6.18$ under Chandra high-angular resolution lens
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• Discovery and characterization of 25 new quasars at 4.6 < z < 6.9 from wide-field multi-band surveys
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• No strong radio absorption detected in the low-frequency spectra of radio-loud quasars at z > 5.6
• High-$z$ radio Quasars in RACS I: Selection, identification, and multi-wavelength properties
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