Hα distribution and kinematics in NGC 7252NW. Left: R-band image (greyscale) overlaid with H I  (blue) and Hα (red) emission. H I  contours are the same as in Fig. 9 (top middle). The outer Hα contour corresponds to a 10σ detection. The cross shows the H I  dynamical centre determined in Sect. 5.1. Middle: enlarged view of the Hα emission. The circle to the bottom-left shows the Hα beam. Right: PV diagram obtained from the Hα datacube along the two main peaks (dashed line in the middle panel). The vertical line corresponds to the circle in the middle panel. Horizontal lines indicate the H I  systemic velocity of NGC 7252NW (solid) and the velocity range covered by the H I  emission (dashed). The Hα velocity resolution is ~2.3 km s^-1 (see Table 3 for details).