Fig. 5. a (top): We show the ¹²CO(1-0) position-velocity (p-v) diagram along the major axis of NGC 3593 (the common line contours and grey scale is 0.01, 0.035, 0.07, 0.12, 0.17, 0.24 to 0.44Jybeam^-1 by steps of 0.1Jybeam^-1). The empty star markers show the stellar radial velocities given by B96, re-scaled to =630kms^-1. Filled circles denote measurements of the ionized gas velocities obtained by B96 with the same reference. b (bottom): A zoomed view of the ¹²CO(1-0) p-v plot along the X axis defined in Fig. 2b, showing the departure from circular motions () across the one-arm spiral (indicated by the arrow; see text for details).