A long-lasting initiative has been undertaken [in collaboration with A. Renzini (ESO)] with the aim of producing synthetic post-AGB evolutionary tracks to study the effects of theoretical assumptions on observable diagrams (e.g., HR diagram, Mv-age diagram, mass distribution, luminosity function, etc.). By means of the Montecarlo procedure, we explore the parameter space of the assumptions on the evolutionary and population models by studying the effects of the Initial Mass Function (IMF), the Initial Mass-Final Mass Relation, the transition time from the AGB to the PN phases, the amount of envelope mass at the end of the envelope ejection, the planetary nebula lifetime, and the hydrogen- and helium-burning phases of the central stars.
A first important result is that the key element for post-AGB evolution is the
envelope mass at the superwind
quenching [Stanghellini & Renzini (2000)].
Such parameter does not
afford physical prediction, and this may be the very reason why the
comparison between models and data in the realm of the post-AGB
populations have been so unsatisfactory to date (see, for
example, the criticism to the results from the use of the planetary
nebula luminosity function as a secondary distance scale indicator).
Our post-AGB population synthesis code could be used in the future for a full host of different applications. In particular, we foresee its application to check the invariance of the planetary nebula luminosity function for different luminosity cut-offs, IMFs, SFRs, and population metallicity.