SIMBAD references

We have developed a new procedure for the generation of a planetary nebula luminosity function (PNLF), improving on previous work (Mendez et al., 1993A&A...275..534M). The procedure is based, as before, on an exponential central star mass distribution, on H-burning post-AGB evolutionary tracks, and on the avoidance of nebular models for the calculation of nebular fluxes. We have added new post-AGB evolutionary tracks and introduced the following improvements: (1) the imperfect analytical representation of post-AGB evolutionary tracks has been replaced by an interpolation routine giving a better approximation; (2) we have modified the distribution of the intensities of [OIII] λ5007 relative to Hβ, so that it better imitates the observed distribution, which we have taken from data in the Strasbourg-ESO catalogue of Galactic PNs and other sources; (3) we have adjusted the absorbing factor µ along the white dwarf cooling tracks, so as to reproduce the observed PNLF of the Magellanic Clouds and M 31 at fainter magnitudes. In this way we have produced a PNLF which is more consistent with observed PN properties. We use this randomly generated PNLF to: (1) show as convincingly as possible that most PNs in any real population must leak stellar H-ionizing photons; (2) revise our determinations of the parameter µ_max; (3) discuss the shape of the PNLF, hinting at the possible existence of a distinct feature 2 magnitudes fainter than the brightest PNs; (4) attempt estimates of maximum final masses from fits to the PNLFs of the LMC and M 31. There is marginal evidence of a higher maximum final mass in the LMC, but this should be confirmed in other galaxies with recent star formation. A convincing confirmation will require to increase the sample sizes and to extend the PNLFs to at least 1.5mag fainter than the brightest PNs.