The highest redshift quasar at Z = 7.085: A radio-quiet source

Abstract

We present 1-2 GHz Very Large Array A-configuration continuum observations on the highest redshift quasar known to date, the z = 7.085 quasar ULAS J112001.48+064124.3. The results show no radio continuum emission at the optical position of the quasar or its vicinity at a level of ≥3σ or 23.1 μJy beam-1. This 3σ limit corresponds to a rest-frame 1.4 GHz luminosity density limit of L ν, 1.4 GHz < 1.76 × 10 24 W Hz-1 for a spectral index of α = 0, and L ν, 1.4 GHz < 1.42 × 1025 W Hz-1 for a spectral index of α = -1. The rest-frame 1.4 GHz luminosity limits are L rad < 6.43 × 106 L and L rad < 5.20 × 107 L for α = 0 and α = -1, respectively. The derived limits for the ratio of the rest-frame 1.4 GHz luminosity density to the B-band optical luminosity density are and <4.30 for the above noted spectral indices, respectively. Given our upper limits on the radio continuum emission and the radio-to-optical luminosity ratio, we conclude that this quasar is radio-quiet and located at the low end of the radio-quiet distribution of high-redshift (z ≳ 6) quasars. © 2014. The American Astronomical Society. All rights reserved..