The Blueshift of the C IV Broad Emission Line in QSOs

Abstract

For the sample from Ge et al. of 87 low-z Palomar-Green quasi-stellar objects (QSOs) and 130 high-z QSOs (0 < z < 5) with {{H}}β -based single-epoch supermassive black hole masses, we perform a uniform decomposition of the C IV λ1549 broad-line profile. Based on the rest frame defined by the [O III] λ5007 narrow emission line, a medium-strong positive correlation is found between the C IV blueshift and the luminosity at 5100 Å or the Eddington ratio {L}_Bol}/{L}_Edd}. A medium-strong negative relationship is found between the C IV blueshift and C IV equivalent width. These results support the postulation where the radiation pressure may be the driver of C IV blueshift. There is a medium-strong correlation between the mass ratio of C IV-based to {{H}}β -based {M}_BH} and the C IV blueshift, which indicates that the bias for C IV-based {M}_BH} is affected by the C IV profile.