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Title:
Chemical Abundances and Kinematics of the Ring Nebula and Its Halos
Authors:
Guerrero, M. A.; Manchado, A.; Chu, Y.-H.
Publication:
Astrophysical Journal v.487, p.328 (ApJ Homepage)
Publication Date:
09/1997
Origin:
APJ
ApJ Keywords:
ISM: ABUNDANCES, ISM: KINEMATICS AND DYNAMICS, ISM: PLANETARY NEBULAE: INDIVIDUAL NGC NUMBER: NGC 6720
DOI:
10.1086/304582
Bibliographic Code:
1997ApJ...487..328G

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.
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