The Fe II spectrum of Seyfert 1 galaxies and quasars.

The equivalent width of blends of Fe II atoms observed in Seyfert galaxies and quasars are calculated in the visible and UV ranges as a function of optical thickness for electron densities and temperatures. Lines from 2000-8000 A and 40 multiplets have been detected and are due to cascade from odd parity levels near 0-2 eV; the 14 levels considered are listed. Collisional models are invoked for an emission region as a homogeneous slab mechanically heated with constant electron density and temperature. Photoionized models are also examined for predicted Fe II spectra, and the projections of all models are compared to known Fe II spectra for the Seyfert galaxies I Zw 1, PHL 1092, II Zw 136, and 3 C 273. The Fe II emission region is determined to have an electron density in the interval 10 billion-1 trillion/cu cm, a temperature in the 7500-10,000 K range, and high optical thickness in the UV line.