REDSHIFT DIFFERENCES BETWEEN THE BALMER AND [O III] LAMBDA-5007 LINESIN HIGH-REDSHIFT QUASARS

We present near-infrared spectra of four quasars (QSOs) at z similar o r equal to 1.5 containing the redshifted Hot, HP, and [O III] emission lines. The Ha profile in these objects is redshifted on average by 43 0 +/- 170 km s(-1) from the systemic velocity derived from [O III] lam bda 5007. This is considerably larger than the Balmer-line velocity sh ifts measured for low-redshift objects and is consistent with the tren d of increasing redshift differences with increasing continuum luminos ity. The rest-frame ultraviolet lines in these objects show large (sim ilar to 1000 km s(-1)) blueshifts from the systemic velocity, and so t he large redshifts for Ha are consistent with the dependence of these redshift differences on ionization potential. These results also show that the systemic velocities of very luminous QSOs are accurately meas ured only from narrow emission lines.