The correlation between jets and the complex morphology of planetary nebulae

Abstract

Planetary nebulae are clouds of gas and dust resulting from the terminal stages of stars of low and intermediate masses. In spite of common sense, the morphology of these objects is not dominantly spherical. In fact, most of the observed structures are elliptical or bipolar, i.e., have a preferential axis of expansion. Also, in the last 20 years, high-resolution observations have revealed that planetary nebulae exhibit structures at smaller scales, similar to knots and collimated jets, visible mainly in atomic lines of low ionization energy. Asymmetric ejections from the stellar wind in the post-AGB, binary systems, and magnetic fields, have been invoked as the main mechanisms responsible for the observed structures. Unfortunately, the community has not yet determined what processes are dominant. The difficulty in reproducing the observations is due to the inability of current hydrodynamic models to reconstruct maps observable consistently. A new proposal concerning the ejection of jets collimated by the central white dwarf star in the post-AGB can help solve the mystery of the origin of asymmetric morphology. In this paper we propose to study the role of jets in the origin of complex morphologies from a series of hydrodynamic simulations of planetary nebulae expanding, considering various scenarios. (AU)