Constraining the quasar radio-loud fraction at $z\sim 6$ with deep radio observations

Abstract

We carry out a series of deep Karl G. Jansky Very Large Array (VLA) S-band observations of a sample of 21 quasars at $z\sim 6$. The new observations expand the searches of radio continuum emission to the optically faint quasar population at the highest redshift with rest-frame $4400\mathring{\mathrm{A}}$ luminosities down to $3\times 10^{11}{L}_{\odot }$. We report the detections of two new radio-loud quasars: CFHQS J2242+0334 (hereafter J2242+0334) at $z=5.88$ and CFHQS J0227$-$0605 (hereafter J0227$-$0605) at $z=6.20$, detected with 3 GHz flux densities of $87.0\pm 6.3\mu \mathrm{Jy}$ and $55.4\pm 6.7\mu \mathrm{Jy}$, respectively. Their radio \replaced{loudness}{loudnesses} are estimated to be $54.9\pm 4.7$ and $16.5\pm 3.2$, respectively. To better constrain the radio-loud fraction (RLF), we combine the new measurements with the archival VLA L-band data as well as available data from the literature, considering the upper limits for non-detections and \deleted{and} possible selection effects. The final derived RLF is $9.4\pm 5.7\%$ for the optically selected quasars at $z\sim 6$. We also compare the RLF to that of the quasar samples at low redshift and check the RLF in different quasar luminosity bins. The RLF for the optically faint objects is still poorly constrained due to the limited sample size. Our \replaced{result}{results} show no evidence of significant quasar RLF evolution with redshift. There is also no clear trend of RLF evolution with quasar UV/optical luminosity due to the limited sample size of optically faint objects with deep radio observations.

14 pages, 5 figures, accepted for publication in the Astrophysical Journal

References in corpus (25)

• Observational constraints on Cosmic Reionization
• An ultra-luminous quasar with a twelve-billion-solar-mass black hole at redshift 6.30
• Radio-Loudness of Active Galactic Nuclei: Observational Facts and Theoretical Implications
• The Pan-STARRS1 distant z>5.6 quasar survey: more than 100 quasars within the first Gyr of the universe
• The Final SDSS High-Redshift Quasar Sample of 52 Quasars at z>5.7
• Physical properties of 15 quasars at $z\gtrsim 6.5$
• 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
• Signals from the Noise: Image Stacking for Quasars in the FIRST Survey
• 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
• Radio Loud and Radio Quiet Quasars
• Probing the Evolution of IR Properties of z~6 Quasars: Spitzer Observations
• Six more quasars at redshift 6 discovered by the Canada-France High-z Quasar Survey
• Constraining the radio-loud fraction of quasars at z>5.5
• High-resolution VLA Imaging of SDSS Stripe 82 at 1.4 GHz
• The first blazar observed at z>6
• Millimeter and Radio Observations of z~6 Quasars
• A survey of luminous high-redshift quasars with SDSS and WISE II. the bright end of the quasar luminosity function at z ~ 5
• On the origin of radio core emission in radio-quiet quasars
• Discovery of Eight z ~ 6 Quasars in the Sloan Digital Sky Survey Overlap Regions
• Mean and Extreme Radio Properties of Quasars and the Origin of Radio Emission
• Stacking of large interferometric data sets in the image- and uv-domain -- a comparative study
• Evidence for a population of beamed radio intermediate quasars
• Milli-arcsecond imaging of the radio emission from the quasar with the most massive black hole at reionization

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