The interaction of planetary nebulae and their AGB progenitors with the interstellar medium

TL;DR

This study uses 3D hydrodynamic simulations to explore how interactions with the interstellar medium influence the shapes and evolution of planetary nebulae from their AGB progenitors, revealing four interaction stages and common tail structures.

Contribution

It provides a comprehensive model of PN-ISM interaction across different stages, velocities, and densities, highlighting the dominant shaping effects during the AGB phase.

Findings

ISM interaction significantly influences PN outer structures.

Four stages of PN-ISM interaction identified.

Most PNe are predicted to have tail structures.

Abstract

Interaction with the Interstellar Medium (ISM) cannot be ignored in understanding planetary nebula (PN) evolution and shaping. In an effort to understand the range of shapes observed in the outer envelopes of PNe, we have run a comprehensive set of three-dimensional hydrodynamic simulations, from the beginning of the asymptotic giant branch (AGB) superwind phase until the end of the post--AGB/PN phase. A 'triple-wind' model is used, including a slow AGB wind, fast post--AGB wind and third wind reflecting the linear movement through the ISM. A wide range of stellar velocities, mass-loss rates and ISM densities have been considered. We find ISM interaction strongly affects outer PN structures, with the dominant shaping occuring during the AGB phase. The simulations predict four stages of PN--ISM interaction whereby the PN is initially unaffected (1), then limb-brightened in the direction of motion (2), then distorted with the star moving away from the geometric centre (3) and finally so distorted that the object is no longer recognisable as a PN and may not be classed as such (4). Parsec-size shells around PN are predicted to be common. The structure and brightness of ancient PNe is largely determined by the ISM interaction, caused by rebrightening during the second stage; this effect may address the current discrepancies in Galactic PN abundance. The majority of PNe will have tail structures. Evidence for strong interaction is found for all known planetary nebulae in globular clusters.