The abundances and mass distribution of planetary nebulae in the galactic bulge

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Abstract
Relative line intensities in 65 luminous planetary nebulae towards, and probably in, the galactic bulge are presented. The distribution of excitation class is fairly uniform over the whole range from very low to very high ionization levels. Oxygen, nitrogen and helium abundances are derived for 49 objects. The results are consistent with essentially all the planetaries having oxygen abundances close to that of the sun and the galactic disk planetaries. One object appears to be oxygen-deficient by a factor of 20. A few possible super-oxygen-rich candidates are proposed. Between 10 and 20 percent of the bulge planetaries are Type I, providing further evidence for a young component to the population of the galactic bulge. It is proposed that the evolutionary history of the galactic bulge requires a relatively large number of the progenitors of the planetary nebulae to have been formed early in its history, with star formation continuing afterwards at a slower rate, the oxygen abundance remaining close to solar over this period.

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