Self-calibrated images of PSO J0309+27 at 1.5 GHz (left), 5 GHz (centre), and 8.4 GHz (right). The contours are drawn at (−3, 3, 6, 9, 18, 36, 72, and 144) times the off-source noise of each map, which are given in Table B.1. The white colour bar indicates 100 pc in projection at z = 6.1. The restoring Gaussian beam is shown in white in the bottom left corner of each image; north is up, and east is left.