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M. Vestergaard (SAO)
Analyses of the C\,{\sc iv} \,\lambda\,1549 line profile of high redshift (z=1.5\,--\,3.5) quasars show the full line base width to increase with decreasing radio core-dominance. This implies that the high-velocity gas emitting C\,{\sc iv}, and possibly the high-ionization lines in general, is situated close to the accretion disk and has similar dynamics. The results of the analyses also argue against the high-ionization lines originating in e.g.\ a polar outflow or a spherical distribution of broad-line clouds, but support models such as the Disk-Wind model (Murray & Chiang 1995, 1997).
A model is proposed to explain these and previously reported characteristics of radio-loud and radio-quiet quasars, respectively. It is based in part on a slightly modified version of the Disk-Wind scenario, adopted to account for the common properties of the broad-line region in all quasars, in which the broad lines are emitted from the base of winds evaporated off the accretion disk. Radio-loud quasars are, compared to radio-quiet sources, suggested in the model to (1) contain less dust and to (2) have stronger magnetic fields and a faster spinning central black hole. A qualitative scenario is suggested, based on the latter two key properties, to account for the generation and collimation of the relativistic radio-jets observed in radio-loud quasars, and for the lack of such powerful radio emission in radio-quiet ones.
Some theoretical and observational tests of the model are presented.
\bigskip \noindent Murray, N., & Chiang, J 1995, Astrophysical Journal Letters, 454, L105 \\ Murray, N., & Chiang, J 1997, Astrophysical Journal, 474, 91
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