Journal ArticleDOI
The formation of emission lines in quasars and Seyfert nuclei
J. Kwan,Julian H. Krolik +1 more
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In this paper, the photoionization and heating throughout a quasar emission-line cloud optically thick at the Lyman edge are calculated, and the dependence of line strengths on physical conditions is discussed.Abstract:
The photoionization and heating throughout a quasar emission-line cloud optically thick at the Lyman edge are calculated. Photoionization and collisional ionization from excited states of hydrogen are included, which maintain a substantial electron fraction after the exhaustion of Lyman continuum photons halts ground-state photoionization. Observed values are explained for Ly-alpha/H-beta, H-alpha/H-beta, P-alpha/H-alpha, He I 5876/H-beta, O I 8446/H-alpha, and Mg II 2798/H-beta. The dependence of line strengths on physical conditions is discussed, and plotting Fe II/4570/H-beta versus Balmer continuum/H-beta is suggested. Other observations are also suggested, and the degree of asymmetry is given between the forward and backward emission of lines from a finite slab to make possible the use of comparative line profile studies to elucidate cloud kinematics.read more
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Journal ArticleDOI
Variability of active galactic nuclei
TL;DR: In this article, the authors proposed the "accretion disk plus wind" model for radio-quiet active galactic nuclei (AGN) and blazars, which is the most appropriate model at present.
Journal ArticleDOI
An Empirical Ultraviolet Template for Iron Emission in Quasars as Derived from I Zwicky 1
TL;DR: In this paper, the authors present an empirical template spectrum suitable for fitting and subtracting/studying the Fe II and Fe III emission lines in the rest frame ultraviolet spectra of quasars and active galactic nuclei, the first empirical ultraviolet iron template to cover the full range of 1250-3090 A.
Journal ArticleDOI
The Radius-Luminosity Relationship for Active Galactic Nuclei: The Effect of Host-Galaxy Starlight on Luminosity Measurements
Misty C. Bentz,Bradley M. Peterson,Richard W. Pogge,Marianne Vestergaard,Christopher A. Onken,Christopher A. Onken +5 more
TL;DR: In this article, the authors measured the host-galaxy starlight contribution to the continuum luminosity at 5100? through the typical ground-based slit position and geometry used in the reverberation-mapping campaigns.
Journal ArticleDOI
Phenomenology of Broad Emission Lines in Active Galactic Nuclei
TL;DR: In this paper, the authors identify fundamental differences between the profiles of radio-quiet and radio-loud sources as well as differences between high and low ionization lines, especially in the radioquiet majority of AGNs.
Journal ArticleDOI
Elemental Abundances in Quasistellar Objects: Star Formation and Galactic Nuclear Evolution at High Redshifts
Fred Hamann,Gary J. Ferland +1 more
TL;DR: In this article, it was shown that most of the enrichment and star formation must occur before the QSOs "turn on" or become observable, on time scales of 1 Gyr at least at the highest redshifts.
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