Excitation class of nebulae?An evolution criterion?

A principally new quantitative system of the classification of the spectra of planetary nebulae is proposed. Spectral class of excitation class of the nebula p is determined according to the relative intensities of forbidden mission lines (N1 + N2) O III /4686 He II and (N1 + N2) O III/H- beta. The...

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Bibliographic Details
Published in:Astrophysics and space science 1991-07, Vol.181 (1), p.73-88
Main Authors: Gurzadyan, G. A., Egikyan, A. G.
Format: Article
Language:English
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Summary:A principally new quantitative system of the classification of the spectra of planetary nebulae is proposed. Spectral class of excitation class of the nebula p is determined according to the relative intensities of forbidden mission lines (N1 + N2) O III /4686 He II and (N1 + N2) O III/H- beta. The excitation classes are obtained for 142 planetary nebulae of all classes - low (p = 1-3), middle (p = 4-8), and high (p = 9-12/+/). An empirical relationship between excitation class p, as an independent parameter, admit an evolutionary interpretation. It is shown that after reaching the highest class of excitation p = 12(+) the nebulae decrease their class of excitation with the further increases of sizes. (Author)
ISSN:0004-640X
1572-946X
DOI:10.1007/BF00644114