Upper-left: Moment-zero (integrated line intensity, in units of mJy km s⁻¹ kpc⁻²). Upper-right: Moment-one (velocity field, in units of km s⁻¹). For the moment-one map, only regions with a signal-to-noise ratio > 1 are taken into account. The thin black lines trace the 25, 50 and 75 per cent contours of the moment-zero peak intensity. The coordinate system is centred on the AGN position obtained from the HST imaging (Suyu et al. 2013). Lower-left: Overlay of the reconstructed CO (2-1) moment-zero map (red contours) on the optical continuum image (grey scale, Suyu et al. 2013). The source-plane caustics are shown as solid grey lines. Lower-right: One-dimensional rotation curve of the reconstructed CO (2-1) source, displaying a shape typical for disk-like dynamics. The blue solid line represents the rotation curve, corrected for disk inclination of i = 54°.