What Do the Ultraviolet Spectra of Narrow‐Line Seyfert 1 Galaxies Tell Us about Their Broad‐Line Regions?
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CitationKuraszkiewicz, Joanna, Belinda J. Wilkes, Bo?ena Czerny, and Smita Mathur. 2000. “What Do the Ultraviolet Spectra of Narrow‐Line Seyfert 1 Galaxies Tell Us About Their Broad‐Line Regions?” The Astrophysical Journal 542 (2) (October 20): 692–702. doi:10.1086/317013.
AbstractWe study the UV spectra of narrow-line Seyfert 1 (NLSy1) galaxies and compare them with "normal" active galactic nuclei. Similar to their optical lines, the NLSy1s show narrower UV lines. They are also characterized by weaker C IV λ1549 and C III] λ1909 and stronger Al III λ1857 emission. These UV-line properties add to the optical and X-ray properties known to be part of the Boroson & Green eigenvector 1. We show that the steep soft X-rays, which characterize the NLSy1s SEDs, change the equilibrium of the two-phase cloud-intercloud medium, resulting in somewhat higher broad-line region cloud densities, lower ionization parameter, and larger broad-line region radii. These modified conditions can explain the unusual emission-line properties we find in NLSy1. Using a specific model of an accretion disk with corona presented by Witt, Czerny, & Życki, we also show that the steep soft and hard X-ray continua can be explained if the L/LEdd ratios are larger than in "normal" Sy1s/QSOs, strengthening earlier suggestions that the L/LEdd is the physical parameter driving this eigenvector.
Citable link to this pagehttp://nrs.harvard.edu/urn-3:HUL.InstRepos:30212191
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