Theoretical models for H II regions. I. Diagnostic diagrams

We have computed an extensive, homogeneous grid of theoretical photoionization models with conditions appropriate to observed H II regions. This grid has been used to develop a comprehensive set of theoretical diagnostic diagrams for H II regions which employ ratios of prominent emission lines to determine the ionization parameter within the nebula, and the ionization temperature of its exciting star(s). It is also possible to estimate the element-averaged metallicity in the nebula and stars from these diagnostics.