Mz 3, a Multipolar Nebula in the Making

Abstract

The nebula Mz 3 has arguably the most complex bipolar morphology, consisting of three nested pairs of bipolar lobes and an equatorial ellipse. Its three pairs of bipolar lobes share the same axis of symmetry, but have very different opening angles and morphologies: the innermost pair of bipolar lobes shows closed lobe morphology, while the other two have open lobes with cylindrical and conical shapes, respectively. We have carried out high-dispersion spectroscopic observations of Mz 3, and detected distinct kinematic properties among the different morphological components. The expansion characteristics of the two outer pairs of lobes suggest that they originated in an explosive event, whereas the innermost pair of lobes resulted from the interaction of a fast wind with the surrounding material. The equatorial ellipse is associated with a fast equatorial outflow which is unique among bipolar nebulae. The dynamical ages of the different structures in Mz 3 suggest episodic bipolar ejections, and the distinct morphologies and kinematics among these different structures reveal fundamental changes in the system between these episodic ejections.