Binned amplitude of the ALMA visibilities as a function of the UV distance (u² + v²). The [C II] visibilities are shown on the left (green) and the [N II] visibilities are shown on the right (red). Observed visibilities are displayed as filled circles with error bars; for clarity, the visibilities on long baselines, which have large uncertainties, are not displayed. The best-fit models obtained in this paper (from the image-domain analysis) are shown as solid lines (green for [C II], red for [N II]). For comparison purposes, on each panel, the model of the other line is also displayed, but re-normalized to fit the observed visibilities. The 1σ confidence interval of the model (determined from our Monte Carlo simulations) is shown as a shaded region in the background.