Modeling and distance determination of planetary nebulae

We have developed a self-consistent method to determine the physical parameters of planetary nebulae (PN) and also their distances using the photo-ionization code CLOUDY. To constrain the models, observed emission line ratios, IRAS fluxes, radio fluxes and angular diameters are used. The method has been tested by applying it to artificial data from a planetary nebula model. It can reproduce all distance independent physical parameters with good accuracy. It can also reproduce the distance and all distance dependent physical parameters, but for this an accurate determination of the angular size is crucial.The method has been further tested by applying it to a sample of five galactic bulge PN. Comparison of the distance independent physical parameters with published data shows that they generally are in fair agreement. The determined distances to these PN have large error margins. However, both the individual distances and the average distance are in agreement with the distance to the galactic bulge.We conclude that the method that is presented works, provided that good observational data are available, and that sufficient emission lines of various ionization stages are observed in the spectrum to constrain the model.