The kinematics of NGC 4361, a Population II planetary nebula with a bipolar outflow

High-resolution, spatially-resolved profiles of Hα, He iiλ6560 and [O iii] λ5007 and deep narrow-band CCD images in the Hα and [O iii] λ5007 emission lines have been obtained of the planetary nebula (PN) NGC 4361. In addition, VLA-DnC λ3.6-cm continuum observations are presented. This material allows one to explore in unprecedented detail the morphology and kinematics of this PN. The morphology of this object is complex given the highly filamentary structure of the envelope, which is confirmed to possess a low mass. The halo has a high expansion velocity that yields incompatible kinematic and evolutionary ages, unless previous acceleration of the nebular expansion is considered. However, the most remarkable result from the present observations is the detection of a bipolar outflow in NGC 4361, which is unexpected in a PN with a Population II low-mass-core progenitor. It is shown that shocks resulting from the interaction of the bipolar outflow with the outer shell are able to provide an additional heating source in this nebula.