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Analysis and Interpretation of Astronomical Spectra 105
E-Class E1-2 E3 E4 E5 E7 E8-12
35,000 50,000 70,000 80,000 90,000 100,000 – 200,000
3. The Expansion of the Nebula
The visibility limit of expanding PN lies at a maximum radius of about 1.6 ly (0.5parsec).
With increasing E-class, also the radius of the expanding nebula is growing. Gurzadyan
[226] provides mean values for [ly] which however may scatter considerably for the
individual nebulae.
E-Class E1 E3 E5 E7 E9 E11 E12+
0.5 0.65 0.72 1.0 1.2 1.4 1.6
22.14 Estimation of Te and Ne with the O III and N II Method
Due to the very weak diagnostic lines, these methods can be applied only to spectra with
high resolution and quality. Further J. Schmoll outlines in his dissertation [201], what influ-
ence the slit width and the method of background subtraction exert on the analysis of weak
lines! The procedure is based on the fundamental equations by Gurzadyan 1997 [10],
which uses for the O III method the lines at λλ 5007, 4959 and 4363, and for the N II
method at λλ 6548, 6584 and 5755.
For the calculation of the electron temperature, these equations can’t be explicitly con-
verted and solved by and contain additionally the variable . But for , empirical formu-
las exist, which are valid for thin gases (typical for H II regions and SNR).
“ “ is the natural logarithm to base e.
For the explicit calculation of , with known , I have converted the formulas {57} {58}
accordingly:
