Left: velocity field at 5′′ resolution. The ellipse shows the modelled disk. The centre, and both the major and the minor axes are shown. The box shows the area covered by the right panel. The circle shows the beam. Contours are the same as in Fig. 2. Right: HST image superimposed with the observed H i  map at 2′′ (black) and the H i  map obtained from a 3D model with i = 70° and z₀ = 100 pc (red). Contours are at 3 (dashed) and 6 (solid)  ×  10²¹ atoms cm^-2. The cross marks the centre and the circle shows the beam.