6.2. Radio-loud versus Radio-quiet
The evidence suggesting that the strength of the BE is related to
source radio properties (Section 2.2) is
worth further consideration
in light of larger trends in quasar phenomenology. Comparative
studies of radio-loud and radio-quiet QSOs have revealed a number of
detailed spectroscopic differences, and some of these disparities may
contribute to the contrast suggested in the Baldwin diagrams. Several
analyses have established that radio-loud quasars display Ly
and C IV lines with narrower profiles and larger average
W
than do radio-quiet sources
(Francis et al. 1993;
Wills et al. 1993a;
Brotherton et al. 1994b;
Corbin & Francis 1994).
Another way of
stating this result is that the emission features for the radio-loud
objects are more dominated by the line core than their radio-quiet
counterparts. If the BE is driven primarily by changes in the line
core (Section 6.1), then objects with
emission lines dominated by the
core component - i.e., the radio-loud objects - might be expected to
show a cleaner correlation, consistent with the putative observational
trend.