The populations of planetary nebulae in the direction of the Galactic bulge - Chemical abundances and Wolf-Rayet central stars

Departamento de Astronomia, Instituto de Astronomia, Geof´isica e Cieˆncias Atmosfe´ricas da USP, Rua do Mata˜o 1226,05508-090, Sa˜o Paulo, BrazilReceived ???; accepted ???Abstract. We have observed 44 planetary nebulae (PNe) in the direction of the Galactic bulge, and merged our data withpublished ones. We have distinguished, in the merged sample of 164 PNe, those PNe most likely to prtain physically to theGalactic bulge and those most likely to belong to the Galactic disk. We have determined the chemical composition of all the164 objects in a coherent way. We looked for stellar emission features and discovered 14 new [WR] stars and 15 new weakemission line central stars.The analyzed data led us to the following conclusions: (1) The spectral type distribution of [WR] stars is very different in thebulge and in the disk of the Galaxy. However, the observed distributions are strongly dependent on selection effects. (2) Theproportion of [WR]PNe is significantly larger in the bulge th an in the disk. (3) The oxygen abundances in [WR] stars do noappear to be significantly a ffected by nucleosynthesis and mixing in the progenitors. (4) The O/H gradient of the Galactic diskPNe population flattens in the most internal parts of the Gala xy. (5) The median oxygen abundance in the bulge PN populationis larger by 0.2 dex than in the disk population seen in the direction of the bulge. (6) Bulge PNe with smaller O/H tend tohave smaller radial velocities. (7) The oxygen abundance distribution of bulge PNe is similar in shape to that of the metallicitydistribution of bulge giants, but significantly narrower. ( 8) The location of SB 32 (PN G 349.7-09.1) in the (V