The Strength of Optical Fe II Emission in Quasi-stellar Objects

Abstract

Based on optical data for a sample of 33 QSOs taken from Wilkes and Elvis, we study the relation between the strength of optical Fe II emission, the line widths, and the soft X-ray spectrum. The previously claimed relation that objects with flat soft X-ray spectra have weak optical Fe II emission is not present for this sample. A strong relation exists that objects with strong optical Fe II emission have narrow Hβ lines. This trend is weaker with Lyα. These relations may be understood if the Fe II line emission is formed in a special zone and has a stronger aspect dependence than the underlying optical continuum.