Source plane reconstruction of C I (1 → 0), CO (J = 4 → 3) and CN (N = 4 → 3) line emission in 9io9. Panels (a)–(g) show the equivalent maps as those displayed in Figure 1 for the image plan, with identical flux density contours. In panels (e) and (f) we show the velocity field from our rotating ring model (Section 3.2) as contours, spanning −350–350 km s−1 in steps of 50 km s−1. CN (N = 4 → 3) does not exhibit a coherent velocity field and is largely unresolved. Red solid lines show the lensing caustic from our best-fitting lens model (Section 3.2).