Optical line profiles of the Helix planetary nebula (NGC 7293) to large radii

TL;DR

This study presents extensive spatially resolved optical emission line profiles of the Helix planetary nebula, revealing multiple bipolar outflows and dynamic ejection processes over 11,000 years.

Contribution

It provides new long-slit observations across the nebula, uncovering complex outflow structures and their kinematic properties, enhancing understanding of planetary nebula evolution.

Findings

NGC 7293 exhibits multiple bipolar outflows along different axes.

Hubble-type outflows are observed over a timescale of 11,000 years.

Ejection events occurred over a short period with varying velocities.

Abstract

New, very long (25'), cuts of spatially resolved profiles of the Halpha and [N II] optical emission lines have been obtained over the face of the Helix planetary nebula, NGC 7293. These directions were chosen to supplement previous similar, though shorter, cuts as well as crossing interesting phenomena in this nebular envelope. In particular one new cut crosses the extremes of the proposed CO J=2-1 emitting outer "torus" shown by Huggins and his co-workers to be nearly orthogonal to its inner counterpart. The second new cut crosses the extensive outer filamentary arcs on either side of the bright nebular core. It is shown that NGC 7293 is composed of multiple bipolar outflows along different axes. Hubble-type outflows over a dynamical timescale of 11,000 years are shown to be occurring for all the phenomena from the smallest He II emitting core out to the largest outer filamentary structure. All must then have been ejected over a short timescale but with a range of ejection velocities