Abundances in planetary nebulae near the galactic centre: I. Abundance determinations

M. A. Ratag, S. R. Pottasch, M. Dennefeld, J. Menzies

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Abstract

Abundance determinations of about 110 planetary nebulae, which are likely to be in the Galactic Bulge are presented. Plasma diagnostics have been performed by making use of the available forbidden line ratios combined with radio continuum measurements. Chemical abundances of He, O, N, Ne, S, Ar, and Cl are then derived by employing theoretical nebular models as interpolation devices in establishing the ionization correction factors (ICFs) used to estimate the distribution of atoms among unobserved ionization stages. The overall agreement between the results derived by using the model-ICFs and those obtained from the theoretical models is reasonably good. The uncertainties related to the total abundances show a clear dependence on the level of excitation. In most cases, the abundances of chlorine can be derived only in objects with a relatively high Cl-abundance. Contrary to the conclusion previously drawn by Webster (1988), we found the excitation classes are not uniformly distributed. A clear peak at about classes 5 and 6 is noticed. The distribution is shifted toward a lower excitation range with respect to that of the nearby nebulae, reflecting the difference in the central star temperature distribution between the two samples.

Original languageEnglish
Pages (from-to)297-310
Number of pages14
JournalAstronomy & astrophysics supplement series
Volume126
Issue number2
DOIs
Publication statusPublished - Dec-1997

Keywords

  • planetary nebulae
  • ISM, abundances
  • galaxy, center
  • LTE MODEL ATMOSPHERES
  • CHEMICAL EVOLUTION
  • ELECTRON TEMPERATURES
  • CENTRAL STARS
  • OXYGEN ABUNDANCE
  • GASEOUS NEBULAE
  • SPIRAL GALAXIES
  • BAADES WINDOW
  • GRADIENT
  • EMISSION

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