On the O III/O II Problem in Medium and High Excitation Planetary Nebulae

Che, A.; Koeppen, J.

doi:10.1007/978-94-009-7094-6_22

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“…When the He  λ4686 line was too weak to be measured, we determined its upper limit so as to derive an upper limit to the temperature of the central star. These cases correspond to T marked with b in Table 1 Che & Köppen 1983) In the other cases, models with different nebular radii were built. For these PNe we found the smallest and the largest radius for which the model converged.…”

Section: The Modelling Proceduresmentioning

confidence: 99%

“…The optical depth of the nebula is derived from the hydrogen ionization structure predicted by the is not only sensitive to the size of the nebula, but it also depends also on several other parameters, mainly on the density distribution (cf. Che & Köppen 1983). When T is derived from the upper limit of the He  λ4686 line, only an upper limit to the helium and other metal abundances can be derived.…”

Section: The Modelling Proceduresmentioning

confidence: 99%

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Chemical abundances of Planetary Nebulae in M 33

Magrini¹,

Perinotto²,

Mampaso

et al. 2004

A&A

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Abstract. Using spectroscopic data presented in Magrini et al. (2003), we have analyzed with the photoionization code CLOUDY 94.00 (Ferland et al. 1998) (Vílchez et al. 1988). Further studies in the outer parts of M 33 are however needed to ascertain this point. The present result shows that oxygen and helium abundances (with lower accuracy also nitrogen, argon and sulphur) can be actually estimated from the brightest PNe of a galaxy, even if the electron temperature cannot be measured. We also found that the oxygen abundance is quite independent of the absolute magnitude of the PN and consequently the brightest PNe are representative of the whole PN population. This represents an important tool for measuring the metallicity of galaxies at the time of the formation of PNe progenitors.

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Section: The Modelling Proceduresmentioning

confidence: 99%

Section: The Modelling Proceduresmentioning

confidence: 99%