Probing the Origins of the CIV and Fe Kalpha Baldwin Effect
  We use UV/optical and X-ray observations of 272 radio-quiet Type 1 AGNs and
quasars to investigate the CIV Baldwin Effect (BEff). The UV/optical spectra
are drawn from the Hubble Space Telescope, International Ultraviolet Explorer
and Sloan Digital Sky Survey archives. The X-ray spectra are from the Chandra
and XMM-Newton archives. We apply correlation and partial-correlation analyses
to the equivalent widths, continuum monochromatic luminosities, and alpha_ox,
which characterizes the relative X-ray to UV brightness. The equivalent width
of the CIV 1549 emission line is correlated with both alpha_ox and luminosity.
We find that by regressing l_UV with EW(CIV) and alpha_ox, we can obtain
tighter correlations than by regressing l_UV with only EW(CIV). Both
correlation and regression analyses imply that l_UV is not the only factor
controlling the changes of EW(CIV); alpha_ox (or, equivalently, the soft X-ray
emission) plays a fundamental role in the formation and variation of CIV.
Variability contributes at least 60% of the scatter of the EW(CIV)-l_UV
relation and at least 75% of the scatter of the of the EW(CIV)-alpha_ox
relation.
  In our sample, narrow Fe Kalpha 6.4 keV emission lines are detected in 50
objects. Although narrow Fe Kalpha exhibits a BEff similar to that of CIV, its
equivalent width has almost no dependence on either alpha_ox or EW(CIV). This
suggests that the majority of narrow Fe Kalpha emission is unlikely to be
produced in the broad emission-line region. We do find suggestive correlations
between the emission-line luminosities of CIV and Fe Kalpha, which could be
potentially used to estimate the detectability of the Fe Kalpha line of quasars
from rest-frame UV spectroscopic observations.
