Velocity centroid (left) and dispersion (right) maps generated using the SoFiA software for the medium-resolution H I image. The green crosses labeled “NW” and “SE” mark the positions of the NW and SE nuclei as seen in the EVN radio continuum images (Figs. 2 and 3). Here, “NW” corresponds to the NW1 component in those EVN images. The dashed black line indicates the major axis identified by the SoFiA software for extracting the PV diagram. The corresponding dynamical center is shown in Fig. A.1.