High-resolution imaging and the H-R diagram of Galactic bulge planetary nebulae

Images of six Galactic PNe in the forbidden O III 5007 line obtained with unprecedented resolution are compared here with those obtained at radio wavelengths. A self-consistent photoionization model obtained using optical spectrophotometry is used to derive chemical abundances and to place the central stars on the H-R diagram. The results are similar to those obtained with the classical Zanstra technique, but with the advantage that objects with high or low temperature central stars can be studied with equal ease. A wide range of metallicity is found which shows that the objects currently passing through the PN phase in the Galactic bulge were born both during and after the collapse of the Galaxy.