LY-ALPHA FLUORESCENT EXCITATION OF FE-II IN ACTIVE GALACTIC NUCLEI

We have calculated Fe II emission-line strengths for active galactic n uclei broad-line regions using precise radiative transfer and Iron Pro ject atomic data. We improve the treatment of all previously considere d excitation mechanisms for the Fe II emission, continuum fluorescence , collisional excitation, fluorescence by self-overlap among the iron lines, and fluorescent excitation by Ly alpha. We demonstrate that Ly alpha fluorescence is of fundamental importance in determining the str ength of the Fe II emission. In addition to enhancing the ultraviolet and optical Fe II flux, Ly alpha fluorescence also results in signific ant near-infrared Fe II emission in the 8500-9500 Angstrom wavelength range. New observations are suggested to probe this effect in strong F P II-emitting quasars.