INTERNAL REDSHIFT DIFFERENCE AND CENTRAL MASS IN QSOS

The redshifts of broad Hβ and narrow [O III] emission lines are measured and compared in 31 low-redshift QSOs with weak or absent optical Fe II features. The redshifts are often not the same for the broad and narrow lines. The distribution of peak redshift differences for our sample is centered near zero. At larger widths the distribution is skewed, suggesting that Hβ more often shows a higher redshift. A mean redshift difference at FWHM of ∼300 km s-1 is found between broad Hβ and the narrow [O III] lines. This value appears to set an upper limit to the central mass, on the order of 109 M⊙, and further to imply the dominance of radiative acceleration in the broad line region of these QSOs.