Astron. Astrophys. Suppl. Ser.
Volume 126, Number 2, December I 1997
|Page(s)||297 - 310|
|Published online||15 December 1997|
Abundances in planetary nebulae near the galactic centre *,**
I. Abundance determinations
Kapteyn Astronomical Institute, Groningen University, Postbus 800, 9700 AV Groningen, The Netherlands
2 Indonesian National Institute of Aeronautics and Space (LAPAN), Jakarta, Indonesia
3 Institut d'Astrophysique, 98bis Boulevard Arago, F–75014 Paris, France
4 South African Astronomical Observatory, P.O. Box 9, Cape Town, South Africa
Send offprint request to: S.R. Pottasch
Accepted: 18 November 1997
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.
Key words: planetary nebulae / ISM: abundances / Galaxy: center
Tables 1 and 2 are published only electronically via the CDS at anonymous ftp 126.96.36.199 or http://cdsweb.u-strasbg.fr/Abstract.html
© European Southern Observatory (ESO), 1997