A Morpho-kinematic And Spectroscopic Study Of The Bipolar Nebulae: M 2𕒽, Mz 3, And Hen 2�

Context. Complex bipolar shapes can be generated either as a planetary nebula or a symbiotic system. The origin of the material ionised by the white dwarf is very different in these two scenarios, and it complicates the understanding of the morphologies of planetary nebulae.
Aims. The physical properties, structure, and dynamics of the bipolar nebulae, M 2𕒽, Mz 3, and Hen 2�, are investigated in detail with the aim of understanding their nature, shaping mechanisms, and evolutionary history. Both a morpho-kinematic study and a spectroscopic analysis, can be used to more accurately determine the kinematics and nature of each nebula.

Methods. Long-slit optical echelle spectra are used to investigate the morpho-kinematics of M 2𕒽, Mz 3, and Hen 2�. The morpho-kinematic modelling software SHAPE is used to constrain both the morphology and kinematics of each nebula by means of detailed 3D models. Near-infrared (NIR) data, as well as optical, spectra are used to separate Galactic symbiotic-type nebulae from genuine planetary nebulae by means of a 2MASS J−H/H−Ks diagram and a �/Hγ vs. �/Hβ diagnostic diagram, respectively. Results. The best-fitted 3D models for M 2𕒽, Mz 3, and Hen 2� provide invaluable kinematical information on the expansion velocity of its nebular components by means of synthetic spectra. The observed spectra match up very well with the synthetic spectra for each model, thus showing that each model is tightly constrained both morphologically and kinematically. Kinematical ages of the different structures of M 2𕒽 and Mz 3 have also been determined. Both diagnostic diagrams show M 2𕒽 and Hen 2� to fall well within the category of having a symbiotic source, whereas Mz 3 borders the region of symbiotic and young planetary nebulae in the optical diagram but is located firmly in the symbiotic region of the NIR colour−colour diagram. The optical diagnostic diagram is shown to successfully separate the two types of nebulae, however, the NIR colour−colour diagram is not as accurate in separating these objects.

Conclusions. The morphology, kinematics, and evolutionary history of M 2𕒽, Mz 3, and Hen 2� are better understood using the interactive 3D modelling tool shape. The expansion velocities of the components for each nebula are better constrained and fitted with a vector field to reveal their direction of motion. The optical and NIR diagnostic diagrams used are important techniques for separating Galactic symbiotic-type nebulae from genuine planetary nebulae.