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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 Lyalpha and C IV lines with narrower profiles and larger average Wlambda 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.