Christophe Morisset (Instituto de Astronomia-UNAM, Mexico)
In this talk I will present a review on the determination of oxygen abundance from photoionization models of nebulae. I will first describe the way models are performed using photoionization codes, explaining the necessary ingredients (inputs) and results (outputs), and the hidden but fundamental atomic data. I will also compare the results (especially the abundances, but also the temperature and density) obtained by photoionization models to the ones obtained by direct methods. I will illustrate the talk showing examples of models, focusing on the convergence process and on some limits of the method.