Abstract
view Abstract Citations (71) References (21) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Asymmetries of the emission lines of QSOs, Seyfert galaxies, and novae. Ferland, G. J. ; Netzer, H. ; Shields, G. A. Abstract Calculations of the anisotropy of line emission from photoionized clouds, and the resulting asymmetry in the line profiles are discussed. The permitted emission-line profiles of Seyfert galaxies and QSO's often contain more light in the red than in the violet wing, and this asymmetry can arise from self-absorption of the line radiation in an expanding system of optically thick clouds. It is shown that the Balmer line optical depths are large enough to give strongly asymmetric line profiles for pure expansion, but the observed lack of strong asymmetry in the Balmer lines of most Seyfert galaxies suggests that the broad-line widths may result from random motions, or that clouds radiate isotropically. It is concluded that the frequently observed absorption of the violet wing of Lyman-alpha must occur in a surrounding region undergoing systematic outflow, or that the weakness of the Balmer line asymmetries is explained by the Balmer line emission resulting from collisional excitation from n=2. Publication: The Astrophysical Journal Pub Date: September 1979 DOI: 10.1086/157297 Bibcode: 1979ApJ...232..382F Keywords: Emission Spectra; Novae; Quasars; Seyfert Galaxies; Spectrum Analysis; Absorption Spectra; Asymmetry; Balmer Series; Lyman Alpha Radiation; Optical Density; Photoionization; Self Absorption; Astrophysics; Line Profiles:Novae; Line Profiles:Quasars; Line Profiles:Seyfert Galaxies; Nova V1500 Cygni; Nova Cygni 1975 full text sources ADS |
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