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 $\ge 3\sigma$ or $23.1\mu$Jy beam${}^{-1}$. This $3\sigma$ limit corresponds to a rest frame 1.4 GHz luminosity density limit of $L_{\nu ,1.4GHz}<1.76\times 10^{24}$ W Hz${}^{-1}$ for a spectral index of $\alpha =0$, and $L_{\nu ,1.4GHz}<1.42\times 10^{25}$ W Hz${}^{-1}$ for a spectral index of $\alpha =-1$. The rest-frame 1.4 GHz luminosity limits are $L_{rad}<6.43\times 10^6{L}_{\odot }$ and $L_{\mathrm{rad}}<5.20\times 10^7{L}_{\odot }$ for $\alpha =0$ and $\alpha =-1$, respectively. The derived limits for the ratio of the rest frame 1.4 GHz luminosity density to the $B$-band optical luminosity density are $R{}_{1.4}^{\ast }<0.53$ 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 ($z\gtrsim 6$) quasars.

11 pages, 3 figures, accepted for publication in AJ

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