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Broad Fe II emission is a prominent feature of the optical and ultravioletspectra of quasars. We report on a systematical investigation of optical Fe IIemission in a large sample of 4037 z < 0.8 quasars selected from the SloanDigital Sky Survey. We have developed and tested a detailed line-fittingtechnique, taking into account the complex continuum and narrow and broademission-line spectrum. Our primary goal is to quantify the velocity broadeningand velocity shift of the Fe II spectrum in order to constrain the location ofthe Fe II-emitting region and its relation to the broad-line region. We findthat the majority of quasars show Fe II emission that is redshifted, typicallyby ~ 400 km/s but up to 2000 km/s, with respect to the systemic velocity of thenarrow-line region or of the conventional broad-line region as traced by theHbeta line. Moreover, the line width of Fe II is significantly narrower thanthat of the broad component of Hbeta. We show that the magnitude of the Fe IIredshift correlates inversely with the Eddington ratio, and that there is atendency for sources with redshifted Fe II emission to show red asymmetry inthe Hbeta line. These characteristics strongly suggest that Fe II originatesfrom a location different from, and most likely exterior to, the region thatproduces most of Hbeta. The Fe II-emitting zone traces a portion of thebroad-line region of intermediate velocities whose dynamics may be dominated byinfall.

A Systematic Analysis of Fe II Emission in Quasars: Evidence for Inflow to the Central Black Hole