Morpho-kinematics of the planetary nebula NGC 3242: an analysis beyond its multiple-shell structure

Abstract

In this paper we present the results of optical high-resolution imaging and spectroscopy of the complex planetary nebula (PN) NGC 3242. Our study is based on the analysis of the narrow-band Hα λ6563, [O III] λ5007, [N II] λ6584, and [S II] λ6724 Å images, and high-resolution spectroscopy using spectral ranges centred on the Hα λ6564, [N II] λ6583, and [O III] λ5007 Å. We detected and analysed morphological components beyond the multiple-shell structure of this PN, to investigate the small-scale morphological components aligned towards its major axis (such as knots and ansae, as well as the arc-like features) and its surroundings. Thus, we investigated the morpho-kinematical properties of NGC 3242, as well as their nature and formation. Our results regarding the elliptical double-shell structure and the distance to this nebula are in concordance with previous studies. Furthermore, we have used the software SHAPE to construct a 3D model of NGC 3242, allowing us to successfully reproduce our observational data. We conclude that the prominent knots emitting in the [N II] line are fast, low-ionization emission regions related to high-velocity jets and the so-called ansae-like features rather resemble bubbles. The disruptions immersed in the halo, whose emission was detected in the [O III] high-excitation emission line, remarkably display high velocities and were formed likely in an earlier ejection event, in comparison to the innermost low-ionization structures and bubbles. Finally, according to our model, the kinematical ages of the structures in NGC 3242 range from 390 to 5400 yr.