Chemical Abundances and Kinematics of the Ring Nebula and Its Halos
Abstract
We have obtained new narrowband CCD images, spatially resolved intermediate- and high-dispersion spectroscopic observations of the Ring Nebula (NGC 6720). These data reveal that the bright main nebula is not a real ring, but a closed shell. A prolate ellipsoidal geometry for this shell is inferred from the observed tilts in the [N II] velocity ellipses at different position angles. The shell has enhanced densities near the equator; the shell surface is fragmented with protruding bubbles and outflows. The high-resolution spatially resolved echellograms allow us to identify the kinematic components associated with small-scale morphological features. The morphologically identified inner and outer halos show neither distinct kinematic discontinuity at the transition nor different chemical abundances, indicating that they have a common origin, the red giant wind.
The kinematic and chemical properties of the Ring Nebula do not support the hypothesis that the Ring is a nearly pole-on bipolar nebula. We propose that the Ring Nebula contains a bubbling prolate ellipsoidal shell and a halo of remnant red giant wind, and that the combination of a nonisotropic excitation and the interaction of the main shell's bubbles and outflows with the surrounding red giant wind produces the petal-like morphology in the inner halo.- Publication:
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The Astrophysical Journal
- Pub Date:
- September 1997
- DOI:
- 10.1086/304582
- Bibcode:
- 1997ApJ...487..328G
- Keywords:
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- ISM: Abundances;
- ISM: Kinematics and Dynamics;
- ISM: Planetary Nebulae: Individual: NGC Number: NGC 6720