Moment zero images (left-hand panels) and difference images (right-hand panel) for the moment zero image and its 180° rotated version. The black crosses indicate the optical centres of the galaxies. The Asymmetry values measured in Holwerda et al. (2011b) for all three examples have a maximum of 1, which indicates that the galaxies are highly asymmetric. The difference do not show signs for strong asymmetries.