Quasar -- CIV forest cross-correlation with SDSS DR12
  We present a new determination of the large-scale clustering of the CIV
forest (i.e., the absorption due to all CIV absorbers) using its
cross-correlation with quasars in the Sloan Digital Sky Survey (SDSS) Data
Release 12 (DR12). We fit a linear bias model to the measured
cross-correlation. We find that the transmission bias of the CIV forest,
$b_{Fc}$, at a mean redshift of $z=2.3$, obeys the relation $(1+\beta_c)b_{F c}
= -0.024 \pm 0.003$. Here, $\beta_{c}$ is the linear redshift space distortion
parameter of the CIV absorption, which can only be poorly determined at
$\beta_c=1.1\pm 0.6$ from our data. This transmission bias is related to the
bias of CIV absorbers and their host halos through the effective mean optical
depth of the CIV forest, $\bar\tau_c$. Estimating a value $\bar \tau_c(z)
\simeq 0.01$ from previous studies of the CIV equivalent width distribution,
our measurement implies a CIV absorber bias near unity, with a large error due
to uncertainties in both $\beta_c$ and $\bar\tau_c$. This makes it compatible
with the higher DLA bias $b_{\rm DLA}\simeq 2$ measured previously from the
cross-correlation of DLAs and the Lyman-$\alpha$ forest. We discuss the
implications of the CIV absorber bias for the mass distribution of their host
halos. More accurate determinations of $\bar \tau_c(z)$ and $\beta_c$ are
necessary to obtain a more robust measurement of this CIV absorber bias.
