IC 5217 as a double-shell, point-symmetric planetary nebula with a very narrow waist

Abstract

Aims. Identification of the structural components and analysis of the internal kinematics in the planetary nebula IC 5217. Methods. Narrow-band images and high resolution long-slit spectra in the Hα ,[ Nii ]a nd [Oiii] emission lines, and VLA 6 cm continuum data. Results. IC 5217 is composed of a very bright equatorial ring, open bipolar lobes, off-axis point-symmetric features, on-axis distant faint regions, and an off-axis very elongated bipolar structure. The ring, open lobes, point-symmetric features and distant faint regions appear as elements of a single point-symmetric bipolar shell with a very narrow waist. This shell presents an axis ratio of ∼37 and an aspect ratio of ∼5. The 6 cm data show that the ring is an extremely flat disk with a central hole. Expansion velocity in the ring ranges from ≤10 km s −1 in He ii up to � 27 km s −1 in [N ii], whereas a velocity of ∼460 km s −1 is estimated for the polar regions of the bipolar shell. Strong acceleration of the outer regions of the ring is observed. The elongated bipolar structure probably represents a highly collimated (aspect ratio ∼12), high velocity cylindrical-like shell. A collimated agent (wind or jet) would account for the shaping of the bipolar shell if this agent has operated in the direction perpendicular to the equatorial disk. The point-symmetric features and cylindrical shell are probably related to collimated ejections but that occurred when the basic nebular shape had already been established.