The kinematics of point-symmetric planetary nebulae

Four planetary nebulae (PNe) with conspicuous point-symmetric morphology are studied in this paper through high-quality imagery and long-slit echelle spectroscopy. Point symmetry is also found in the velocity space, and this is related to particular forms of bipolar collimated outflows. Morphology and kinematics together reveal the presence of collimated bipolar ejections in an episodic way with indications of rotation or displacement of the symmetry axis of the outflow. Point symmetry is currently known to occur in a wide variety of PNe and the convenience of a reevaluation of point-symmetric PNe as a main morphological class is pointed out.