The outflows and 3D structure of NGC 6337, a planetary nebula with a close binary nucleus

TL;DR

This study provides a detailed 3D model of NGC 6337, revealing complex kinematics, bipolar outflows, and the influence of a close binary nucleus on the nebula's structure and outflow dynamics.

Contribution

It introduces a comprehensive 3D morphological and kinematic model of NGC 6337, highlighting the effects of a close binary nucleus on nebular outflows and structure.

Findings

A slowly expanding toroid with density fluctuations

Bipolar expanding caps of low ionization outside the toroid

High velocity bipolar collimated outflow with precession or rotation evidence

Abstract

NGC 6337 is a member of the rare group of planetary nebulae where a close binary nucleus has been identified. The nebula's morphology and emission line profiles are both unusual, particularly the latter. We present a thorough mapping of spatially resolved, long-slit echelle spectra obtained over the nebula that allows a detailed characterization of its complex kinematics. This information, together with narrow band imagery is used to produce a three dimensional model of the nebula using the code SHAPE. The 3-D model yields a slowly expanding toroid with large density fluctuations in its periphery that are observed as cometary knots. A system of bipolar expanding caps of low ionization are located outside the toroid. In addition, an extended high velocity and tenuous bipolar collimated outflow is found emerging from the core and sharply bending in opposite directions, a behavior that cannot be accounted for by pure magnetic launching and collimation unless the source of the outflow is precessing or rotating, as could be expected from a close binary nucleus.