Theoretical FeI/II/III Emission-Line Strengths from Active Galactic Nuclei with Broad-Line Regions

Abstract

We present theoretical iron emission line strengths for physical conditions typical of Active Galactic Nuclei with Broad-Line Regions. The non-local thermodynamic equilibrium (NLTE) models include a new and extensive treatment of radiative transfer in the FeIII ion, complementing the FeII emission line strengths predicted in our earlier works. We also briefly present preliminary results for the FeI emission from AGN using a reduced atom model. We can satisfactorily reproduce the empirical UV FeIII emission line template of Vestergaard & Wilkes (2001) for the prototypical narrow-line Seyfert 1 galaxy I Zw 1, both in terms of the general FeIII flux distribution and the relative strength of the FeIII and FeII emission. However, a number of detailed features are still not matched; the most prominent example is the strongest single FeIII feature observed in the I Zw 1 spectrum, UV47: it is predicted to be strong only in models suppressing Fe-H charge exchange reactions. We examine the role of variations in cloud turbulent velocity and iron abundance and carry out Monte Carlo simulations to demonstrate the effect of uncertainties in atomic data on the computed spectra.