FITTING PHOTOIONIZATION MODELS TO PLANETARY NEBULAE
| Autor: | J. Bohigas |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2009 |
| Předmět: | |
| Zdroj: | Universidad Nacional Autónoma de México UNAM Redalyc-UNAM Revista Mexicana de Astronomía y Astrofísica (México) Vol.35 |
| Popis: | "Good to excellent photoionization models based on the Cloudy code were obtained for 13 out of 19 spectra of planetary nebulae. The two most important assumptions are that the photoionizing continuum is a Rauch model star, with gravity set by the condition that the stellar mass must be ? 1 M, and density is constant and determined from the observed [S II]6717/6731 ratio. The temperature and luminosity of the central star, the inner radius of the nebula and the abundance of carbon are treated as free parameters in each model run, destined to obtain the best possible t to the relative intensities of He II 4686, [O III]5007 and [N II]6584. Observed and modeled nebular temperatures derived from [N II] (6548+6584) /5755 agree within 10%, but models usually underestimate temperatures found from [O III] (4959+5007) /4363, more so when the slit does not cover the in-depth extent of the ionized region. Helium, nitrogen, oxygen, neon, sulfur and argon model abundances are uncertain at the 15%, 15%, 10%, 7%, 30% and 7% level. It is shown that neon abundance in PNe has been consistently overestimated, and an alternative ionization correction factor is recommended." |
| Databáze: | OpenAIRE |
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