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A&A Supplement Series, Vol. 126, December I 1997, 297-310

Received July 29, 1996; accepted November 18, 1997

Abundances in planetary nebulae near the galactic centregifgif

I. Abundance determinations

M.A. Ratagtex2html_wrap1763 - S.R. Pottaschtex2html_wrap1765 - M. Dennefeld tex2html_wrap1767 - J. Menzies tex2html_wrap1769

Send offprint request: S.R. Pottasch
tex2html_wrap529 Kapteyn Astronomical Institute, Gronin gen University, Postbus 800, 9700 AV Groningen, The Netherlands
tex2html_wrap529  Indonesian National Institute of Aeronautics and Space (LAPAN), Jakarta, Indonesia
tex2html_wrap531  Institut d'Astrophysique, 98bis B oulevard Arago, F-75014 Paris, France
tex2html_wrap533  South African Astronomical Observ atory, P.O. Box 9, Cape Town, South Africa


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.

keywords: planetary nebulae -- ISM: abundances -- Galaxy: center

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