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W.-H. Sun, Y.-W. Cheng (National Central University)
It has long been recognized that the redshifts inferred from the centroids of certain broad emission lines are each different from the systemic redshift averaged over measurements of narrow emission lines in many QSOs and AGNs. In this work, we examined the temporal behavior of H-beta line profile of a sample of Seyfert 1 galaxies in the International AGN Watch data archive. The narrow components, assumed constant, were fitted and removed. The varying broad components were then fitted with Gausian line models. In particular in NGC 5548 over a period of 5 years (1988-1993), the redshifts inferred from the centroids of the best-fit Gaussians show clear blue- and red-shifted differences from the averaged emission line redshift. These redshift differences in time seem to be inversely correlated with the variations of continuum brightness. We interpret this inverse correlation as line-of-sight motions of BLR clouds driven by gravity and radiation pressure from the central continuum source.
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The author(s) of this abstract have provided an email address for comments about the abstract: sun@jade.astro.ncu.edu.tw