Catching a grown-up starfish planetary nebula - I. morpho-kinematical study of PC 22

© 2017 The Authors. We present the first part of an investigation on the planetary nebula (PN) PC 22 that focuseson the use of deep imaging and high-resolution echelle spectroscopy to perform a detailedmorpho-kinematical analysis. PC 22 is revealed to be a multipolar PN emitting predominantlyin [O III] and displaying multiple non-symmetric outflows. Its central region is found to be alsoparticularly inhomogeneous with a series of low-ionization structures (knots) located on thepath of the outflows. The morpho-kinematical model obtained with SHAPE indicates that (i) thede-projected velocities of the outflows are rather large, ≥100 km s-1, while the central regionhas expansion velocities in the range ∼25 to ∼45 km s-1following the 'Wilson effect'; (ii) themajority of the measured structures share similar inclination, ≃100°, i.e. they are coplanar;(iii) and all outflows and lobes are coeval (within the uncertainties). All these results make usto suggest that PC 22 is an evolved starfish PN.We propose that the mechanism responsible forthe morphology of PC 22 consists of a wind-shell interaction, where the fast post-asymptoticgiant branch (AGB) wind flows through a filamentary AGB shell with some large voids.