Abstract
A technique for self-consistent determination of the mass of ionized gas M i in planetary nebulae (PNe) envelopes and the distance D to these nebulae is developed. The technique is based on the calculation of optimized photoionization models of their emission (OPMEs). Models of a “young” nebula (IC 5117) and an “old” one (NGC 7293) are calculated. The values M i = 0.0056M ⊙ and D = 1287 pc for IC 5117 and M i = 0.681M ⊙ and D = 201 pc for NGC 7293 are determined. The radial gas density distribution in a PN envelope was defined by an approximation expression that is close to the “normal” one and was found earlier based on the analysis of isophote maps of 12 PNe (Astron. Zh. 69, 1166–1178 (1992)). The mass of ionized gas in nebulae envelopes was determined in the process of OPME calculation by integrating the radial density distribution over the envelope volume. The distance to nebulae was also determined in the process of OPME calculation as one of its free parameters by comparing the model flux in the Hβ line at a distance to the Earth set by the optimizer with the corresponding observed flux. The values of D determined in such a manner are compared to the data from other studies.
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