Photoionization Modeling and the K Lines of Iron

We calculate the efficiency of iron K line emission and iron K absorption inphotoionized models using a new set of atomic data. These data are morecomprehensive than those previously applied to the modeling of iron K linesfrom photoionized gases, and allow us to systematically examine the behavior ofthe properties of line emission and absorption as a function of the ionizationparameter, density and column density of model constant density clouds. We showthat, for example, the net fluorescence yield for the highly charged ions issensitive to the level population distribution produced by photoionization, andthese yields are generally smaller than those predicted assuming the populationis according to statistical weight. We demonstrate that the effects of the manystrongly damped resonances below the K ionization thresholds conspire to smearthe edge, thereby potentially affecting the astrophysical interpretation ofabsorption features in the 7-9 keV energy band. We show that the centroid ofthe ensemble of K$\alpha$ lines, the K$\beta$ energy, and the ratio of theK$\alpha_1$ to K$\alpha_2$ components are all diagnostics of the ionizationparameter of our model slabsComment: 38 pages, submitted to Ap.J. Sup