CIV emission line properties and uncertainties in black hole mass
  estimates of z ~ 3.5 quasars
  Using a high luminosity ($L_{\rm bol} \sim 10^{47.5} - 10^{48.3}$ erg
s$^{-1}$), high redshift ($3.2 < z < 3.8$) quasar sample of 19 quasars with
optical and near-infrared spectroscopy, we investigate the reliability of the
CIV-based black hole mass estimates ($M_{\rm BH}$). The median logarithm of the
CIV- and H$\beta$-based $M_{\rm BH}$ ratios is 0.110 dex with the scatter of
0.647 dex. The CIV-to-H$\beta$ BH mass differences are significantly correlated
with the CIV FWHMs, blueshifts and asymmetries. Corrections of the CIV FWHM
using the blueshift and asymmetry reduce the scatter of the mass differences by
$\sim$ 0.04-0.2 dex. Quasars in our sample accrete at the Eddington ratio
$R_{\rm EDD}>0.3$ and cover a considerable range of blueshifts, with 18/19 of
the quasars showing CIV blueshifts (with the median value of 1126 km s$^{-1}$)
and 14/19 of the quasars showing CIV blueshifts larger than 500 km s$^{-1}$. It
suggests that not all quasars with high Eddington ratios show large blueshifts.
The Baldwin effect between the CIV rest-frame equivalent width (REW) and the
continuum luminosity at 1350 $\overset{\lower.5em\circ}{\mathrm{A}}$ is not
seen, likely due to the limited luminosity range of our sample. We find a lack
of flux in the red wing of the composite spectrum with larger CIV blueshift,
and detect a higher ratio of [OIII] quasars with REW$_{\rm [OIII]}>5$
$\overset{\lower.5em\circ}{\mathrm{A}}$ in the subsample with lower CIV
blueshift. It is more likely that they are caused by the combination of the
Eddington ratio and the orientation effect.
