EDP Sciences
Free access
Volume 382, Number 1, January IV 2002
Page(s) 282 - 290
Section Diffuse matter in space
DOI http://dx.doi.org/10.1051/0004-6361:20011621

A&A 382, 282-290 (2002)
DOI: 10.1051/0004-6361:20011621

Study of electron density in planetary nebulae

A comparison of different density indicators
M. V. F. Copetti1, 2 and B. C. Writzl1

1  Laboratório de Análise Numérica e Astrofísica, Departamento de Matemática, Universidade Federal de Santa Maria, 97119-900 Santa Maria, RS, Brazil
2  Physics Department, University of Cincinnati, Cincinnati OH 45221-0011, USA

(Received 29 August 2001 / Accepted 7 November 2001)

We present a comparison of electron density estimates for planetary nebulae based on different emission-line ratios. We have considered the density indicators [ $\ion{O}{ii}$] $\lambda$3729/ $\lambda$3726, [ $\ion{S}{ii}$] $\lambda$6716/ $\lambda$6731, [ $\ion{Cl}{iii}$] $\lambda$5517/ $\lambda$5537, [ $\ion{Ar}{iv}$] $\lambda$4711/ $\lambda$4740, $\ion{C}{iii}$] $\lambda$1906/ $\lambda$1909 and [ $\ion{N}{i}$] $\lambda$5202/ $\lambda$5199. The observational data were extracted from the literature. We have found systematic deviations from the density homogeneous models, in the sense that: $N_\mathrm{e}(\ion{N}{i}) \la N_\mathrm{e}(\ion{O}{ii}) <
N_\mathrm{e}(\ion{S}{ii}, \ion{C}{iii}, \ion{Cl}{iii} ~\mathrm{or}~
\ion{Ar}{iv})$ and $N_\mathrm{e}(\ion{S}{ii}) \approx N_\mathrm{e}(\ion{C}{iii}) \approx N_\mathrm{e}(\ion{Cl}{iii}) \approx
N_\mathrm{e}(\ion{Ar}{iv}).$ We argue that the lower [ $\ion{O}{ii}$] density estimates are likely due to errors in the atomic parameters used.

Key words: ISM: planetary nebulae

Offprint request: M. V. F. Copetti, mvfc@lana.ccne.ufsm.br

SIMBAD Objects

© ESO 2002