Improved calculations for the C III 1907,1909 and SI III 1883,1892 electron density sensitive emission-line ratios, and a comparison with IUE observations

Keenan, F. P.; Feibelman, W. A.; Berrington, K A

doi:10.1086/171220

Cited by 79 publications

(54 citation statements)

References 12 publications

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“…Thus, extragalactic planetary nebulae should be investigated as possible probes of the metallicity of the interstellar medium in the internal parts of spiral galaxies as well as in metal-rich elliptical galaxies. Berrington (1985Berrington ( , 1992, Burke et al (1985) Tachiev & Froese Fischer (1999) C IV Kingston & Hibbert ( Froese Fischer & Tachiev (2004a) …”

Section: Discussionmentioning

confidence: 99%

Biases in abundance derivations for metal-rich nebulae

Stasińska¹

2005

A&A

170

211

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Abstract. Using ab-initio photoionization models of giant H  regions, we test methods for abundance determinations based on a direct measurement of the electron temperature, now possible even for moderate to high-metallicity objects. We find that, for metallicities larger than solar, the computed abundances deviate systematically from the real ones, generally by larger amounts for more metal-rich H  regions. We discuss the reasons for this, and present diagrams allowing the reader to better understand the various factors coming into play. We briefly discuss less classical methods to derive abundances in metal-rich H  regions.In particular, we comment on the interest of the oxygen and carbon recombination lines. We also show that, contrary to the case of giant H  regions, the physical conditions in bright extragalactic planetary nebulae are such that their chemical composition can be accurately derived even at high metallicities. Thus, extragalactic planetary nebulae are promising potential probes of the metallicity of the interstellar medium in the internal parts of spiral galaxies as well as in metal-rich elliptical galaxies.

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Section: Discussionmentioning

confidence: 99%

Biases in abundance derivations for metal-rich nebulae

Stasińska¹

2005

A&A

170

211

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“…Electron impact excitation rates for transitions among the above fine-structure levels were obtained from Berrington (1985) and Keenan et al (1992). Einstein A-coefficients for allowed transitions were taken from Froese Fischer (1994), except for the 2s 2 1 S -2s2p 1 P resonance line, where the experimental value of Reistad & Martinson (1986) was adopted.…”

Section: Methodsmentioning

confidence: 99%

Opacity in the upper atmosphere of AU Mic

Bloomfield

Mathioudakis

Christian

et al. 2002

A&A

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Abstract. In this paper we investigate the validity of the optically thin assumption in the transition region of the late-type star AU Mic. We use Far-Ultraviolet Spectroscopic Explorer (FUSE) observations of the C  multiplet and O  resonance lines, hence yielding information at two different levels within the atmosphere. Significant deviations from the optically thin fluxes are found for C  in both quiescent and flare spectra, where only 60% of the flux is actually observed. This could explain the apparent deviation of C  observed in emission measure distributions. We utilize escape probabilities for both homogeneous and inhomogeneous geometries and calculate optical depths as high as 10 for the C  1175.71 Å component of the multiplet. Using a lower limit to the electron density (10 11 cm −3 ) we derive an effective thickness of <100 km for the scattering layer. The emission originates from very small and compact regions, consistent with a filling factor of 10 −5 derived for the flare plasma.

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“…In Figs In the past C iii] densities systematically higher than those from optical ratios had been found (Feibelman et al 1981) in consequence of errors in the C iii] atomic data (Keenan et al 1992). …”

Section: Iii]mentioning

confidence: 96%

Study of electron density in planetary nebulae

Copetti

Writzl

2002

A&A

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Abstract. We present a comparison of electron density estimates for planetary nebulae based on different emissionline ratios. We have considered the density indicators. The observational data were extracted from the literature. We have found systematic deviations from the density homogeneous models, in the sense that:We argue that the lower [O ii] density estimates are likely due to errors in the atomic parameters used.

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Improved calculations for the C III 1907,1909 and SI III 1883,1892 electron density sensitive emission-line ratios, and a comparison with IUE observations

Cited by 79 publications

References 12 publications

Biases in abundance derivations for metal-rich nebulae

Biases in abundance derivations for metal-rich nebulae

Opacity in the upper atmosphere of AU Mic

Study of electron density in planetary nebulae

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