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 ULASÂ 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 \geq 3 \sigma or 23.1 ~ { } \mu Jy beam ^ { -1 } .
This 3 \sigma limit corresponds to a rest frame 1.4Â GHz luminosity density limit of L _ { \nu, 1.4 GHz } < 1.76 \times 10 ^ { 24 } Â WÂ Hz ^ { -1 } for a spectral index of \alpha = 0 , and L _ { \nu, 1.4 GHz } < 1.42 \times 10 ^ { 25 } Â WÂ Hz ^ { -1 } for a spectral index of \alpha = -1 .
The rest-frame 1.4Â GHz luminosity limits are L _ { rad } < 6.43 \times 10 ^ { 6 } ~ { } L _ { \odot } and L _ { 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 \hbox to 0.0 pt { } _ { 1.4 } ^ { * } < 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 .