# The Blueshift Of Civ Broad Emission Line In Qsos

## TL;DR

This study analyzes the blueshift of the extsc{civ} broad emission line in quasars, revealing correlations with luminosity, Eddington ratio, and black hole mass estimates, supporting radiation pressure as a driving mechanism.

## Contribution

It provides a uniform decomposition of extsc{civ} profiles across a large quasar sample and identifies key correlations influencing black hole mass estimates.

## Key findings

- extsc{civ} blueshift correlates with luminosity and Eddington ratio.
- extsc{civ} blueshift negatively correlates with extsc{civ} equivalent width.
- Bias in extsc{civ}-based black hole mass estimates is affected by extsc{civ} profile properties.

## Abstract

For the sample from Ge et al. of 87 low-$z$ Palomar--Green (PG) quasi-stellar objects (QSOs) and 130 high-$z$ QSOs ($0<z<5$) with $\hb$-based single-epoch supermassive black hole (SMBH) masses, we performed a uniform decomposition of the \civ\ $\lambda$1549 broad-line profile. Based on the rest frame defined by the \oiii $\lambda$5007 narrow emission line, a medium-strong positive correlation is found between the \civ\ blueshift and the luminosity at 5100\AA\ or the Eddington ratio \leddR. A medium-strong negative relationship is found between the \civ\ blueshift and \civ\ equivalent width. These results support the postulation where the radiation pressure may be the driver of \civ\ blueshift. There is a medium strong correlation between the mass ratio of \civ-based to $\hb$-based \mbh and the \civ\ blueshift, which indicates that the bias for \civ-based \mbh is affected by the \civ\ profile.