F eb 2 00 6 Fe II and Mg II in Luminous , Intermediate - Redshift Narrow - line Seyfert 1 Galaxies from the Sloan Digital Sky Survey

We present results from analysis of spectra from a sample of ∼ 900 quasars from the Sloan Digital Sky Survey. These objects were selected for their intermediate redshift (1.2 < z < 1.8), placing Mg II and UV Fe II in the optical band pass, relatively narrow Mg II lines, and moderately good signal-to-noiseratio spectra. Using a maximum likelihood analysis, we discovered that there is a significant dispersion in the Fe II/Mg II ratios in the sample. Using simulations, we demonstrate that this range, and corresponding correlation between Fe II equivalent width and Fe II/Mg II ratio, are primarily a consequence of a larger dispersion of Fe II equivalent width (EW) relative to Mg II EW. This larger dispersion in Fe II EW could be a consequence of a range in iron abundance, or in a range of Fe II excitation. The latter possibility is supported by evidence that objects with weak (zero) C II] λ2325 equivalent width are likely to have large Fe II/Mg II ratios. We discuss physical effects that could produce a range of Fe II/Mg II ratio. Subject headings: line: formation — quasars: emission lines