A search for planetary nebulae in M33

We searched for planetary nebulae (PNe) in the nearby spiral galaxy M33 usi ng the Wide Field Camera at the 2.54 m Isaac Newton Telescope of La Palma ( Spain). Images in the [O III] nebular line at lambda 5007 Angstrom, in the H alpha+[N II] lines around 6560 Angstrom, and in the continuum around 5550 Angstrom allowed us to detect a large number of emission line objects. Amo ng them, 134 candidate PNe have been selected. In addition, we found 63 emi ssion-line objects which have a non-negligible continuum emission, and for this reason they have been conservatively discarded from the group of candi date PNe. We have derived the PN luminosity function. It agrees very well w ith that of galaxies in the Local Group. The resulting distance to M33 is 8 40 +/- 90 kpc, in excellent agreement with the value obtained using Cepheid s.