Loading…
The five axes of the Turtle: symmetry and asymmetry in NGC 6210
ABSTRACT We carry out a comprehensive kinematic and morphological study of the asymmetrical planetary nebula: NGC 6210, known as the Turtle. The nebula’s spectacularly chaotic appearance has led to proposals that it was shaped by mass transfer in a triple star system. We study the three-dimensional...
Saved in:
Published in: | Monthly notices of the Royal Astronomical Society 2021-03, Vol.502 (1), p.1070-1094 |
---|---|
Main Authors: | , , , |
Format: | Article |
Language: | English |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Request full text |
Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
Summary: | ABSTRACT
We carry out a comprehensive kinematic and morphological study of the asymmetrical planetary nebula: NGC 6210, known as the Turtle. The nebula’s spectacularly chaotic appearance has led to proposals that it was shaped by mass transfer in a triple star system. We study the three-dimensional structure and kinematics of its shells, lobes, knots, and haloes by combining radial velocity mapping from multiple long-slit spectra with proper motion measurements from multi-epoch imaging. We find that the nebula has five distinct ejection axes. The first is the axis of the bipolar, wind-blown inner shell, while the second is the axis of the lop-sided, elliptical, fainter, but more massive intermediate shell. A further two axes are bipolar flows that form the point symmetric, high-ionization outer lobes, all with inclinations close to the plane of the sky. The final axis, which is inclined close to the line of sight, traces collimated outflows of low-ionization knots. We detect major changes in outflow directions during the planetary nebula phase, starting at or before the initial ionization of the nebula 3500 yr ago. Most notably, the majority of redshifted low-ionization knots have kinematic ages greater than 2000 yr, whereas the majority of blueshifted knots have ages younger than 2000 yr. Such a sudden and permanent 180° flip in the ejection axis at a relatively late stage in the nebular evolution is a challenge to models of planetary nebula formation and shaping. |
---|---|
ISSN: | 0035-8711 1365-2966 |
DOI: | 10.1093/mnras/staa4014 |