Predicted Fe ii Emission‐Line Strengths from Active Galactic Nuclei

Abstract

We present theoretical Fe ii emission line strengths for physical conditions typical of active galactic nuclei with broad-line regions. The Fe ii line strengths were computed with a precise treatment of radiative transfer using extensive and accurate atomic data from the Iron Project. Excitation mechanisms for the Fe ii emission included continuum fluorescence, collisional excitation, self-fluorescence among the Fe ii transitions, and fluorescent excitation by Lyand Ly� . A large Fe ii atomic model consisting of 827 fine structure levels (including states to E � 15 eV) was used to predict fluxes for approximately 23,000 Fe ii transitions, covering most of the UV, optical, and IR wavelengths of astrophysical interest. Spectral synthesis for wavelengths from 1600 Ato 1.2 lm is presented. Applications of present theoretical templates to the analysis of observa- tions are described. In particular, we discuss recent observations of near-IR Fe ii lines in the 8500 A ˚ -1 lm region which are predicted by the Lyfluorescence mechanism. We also compare our UV spectral synthesis with an empirical iron template for the prototypical, narrow-line Seyfert galaxy I Zw 1. The theoretical Fe ii template presented in this work should also be applicable to a variety of objects with Fe ii spectra formed under similar excitation conditions, such as supernovae and symbiotic stars. Subject headings: line: formation — line: identification — quasars: emission lines — supernovae: general On-line material: machine-readable table