Modeling Fe II emission and revised Fe II (UV) empirical templates

We use the narrow-lined broad-line region (BLR) of the Seyfert 1 galaxy, IZw 1, as a laboratory for modeling the ultraviolet (UV) Fe II 2100-3050 angstrom emission complex. We calculate a grid of Fe II emission spectra representative of BLR clouds and compare them with the observed I Zw 1 spectrum. Our predicted spectrum for log n(H)/(cm(-3)) = 11.0, log [Phi(H)/(cm(-2) s(-1)) = 20.5, and xi/( 1 km s(-1)) 20, using Cloudy and an 830 level model atom for Fe II with energies up to 14.06 eV, gives a better fit to the UV Fe II emission than models with fewer levels. Our analysis indicates ( 1) the observed UV Fe II emission must be corrected for an underlying Fe II pseudocontinuum; ( 2) Fe II emission peaks can be misidentified as that of other ions in active galactic nuclei ( AGNs) with narrow-lined BLRs possibly affecting deduced physical parameters; ( 3) the shape of 4200-4700 angstrom Fe II emission in I Zw 1 and other AGNs is a relative indicator of narrow-line region ( NLR) and BLR Fe II emission; ( 4) predicted ratios of Ly alpha, C III], and Fe II emission relative to Mg II lambda 2800 agree with extinction corrected observed I Zw1 fluxes, except for C IV lambda 1549; ( 5) the sensitivity of Fe II emission strength to microturbulence xi casts doubt on existing relative Fe/Mg abundances derived from Fe II ( UV)/Mg II flux ratios. Our calculated Fe II emission spectra, suitable for BLRs in AGNs, are available at http://iacs.cua.edu/people/verner/FeII.