A redshift difference between high and low ionization emission-line regions in QSOs - Evidence for radial motions

The discovery of a systematic difference between the redshifts of the emission lines arising from the different ionization zones of broad-line quasar clouds is reported. The C IV, N V, C III], [Fe X], [Fe X], and possibly Lyman-α lines are at a lower redshift than the 0 1, Mg II, and Balmer lines. Comparison with the redshifts of the narrow emission lines shows that it is the high-ionization broad emission lines that are systematically blueshifted by 600 km s⁻¹. This blueshift together with the high degree of symmetry of the high-ionization lines strongly constrains models of the broad emission line region. The blueshifting of the strongest emission lines readily observable in high-redshift quasars will affect the number of absorption-line systems which appear to have Zabs ≥ Zem.