2000/06/23 by Joanna Kuraszkiewicz, J. Kuraszkiewicz, B. J. Wilkes +3 · 1 citation
Physics and Astronomy · #Accretion (finance) #Accretion disc #Active galactic nucleus #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics and Star Formation Studies #Emission spectrum #Galaxies: Formation, Evolution, Phenomena #Galaxy #Geometry #Ionization #Line (geometry) #Optics #Physics #QSOS #Quasar #Spectral line #Ultraviolet #astro-ph
paper · pdf · doi:10.1086/317013
27 pages, 5 figures, accepted for publication in ApJ
arxiv created 2000/06/23 · openalex publication_date 2000/10/20 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/06
We 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 / L Edd ratios are larger than in "normal" Sy1s/QSOs, strengthening earlier suggestions that the L / L Edd is the physical parameter driving this eigenvector.