Asymmetries of the emission lines of QSOs, Seyfert galaxies, and Novae

Journal Article · Sat Sep 01 04:00:00 EDT 1979 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/157297· OSTI ID:5911078

Ferland, G J; Netzer, H; Shields, G A

The permitted emission-line profiles of Seyfert galaxies and QSOs often contain more light in the red wing than in the violet wing. Such an asymmetry can arise as a consequence of self-absorption of the line radiation in an expanding system of optically thick clouds. Calculations are presented of the anisotropy of line emission from photoionized clouds, and the resulting asymmetry in the line profiles is discussed. This process is shown to have operated in Nova Cygni 1975. For Seyfert galaxies, considerations of Balmer decrements, ionization equilibrium, and the O I lambda8446 emission indicate that the Balmer line optical depths are large enough to give strongly asymmetric line profiles for pure expansion. However, the observed lack of strong asymmetry in the Balmer lines of most Seyfert galaxies suggests that the broad-line widths may result primarily from random motions, or that the clouds radiate isotropically for some reason, perhaps because they are immersed in an extended source of ionizing continuum. In this case, the frequently observed absorption of the violet wing of L..cap alpha.. must occur in a surrounding region undergoing systematic outflow. Alternatively, the weakness of the Balmer line asymmetries can be understood if most of the Balmer line emission results from collisional excitation from n=2.

• Research Organization: McDonald Observatory and Department of Astronomy, University of Texas at Austin
• OSTI ID: 5911078
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 232:2; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
BALMER LINES
COSMIC RADIO SOURCES
ELEMENTARY PARTICLES
EMISSION SPECTRA
ERUPTIVE VARIABLE STARS
GALAXIES
IONIZATION
LINE WIDTHS
MASSLESS PARTICLES
NOVAE
PHOTOIONIZATION
PHOTONS
QUASARS
RADIATION TRANSPORT
SEYFERT GALAXIES
SPECTRA
STARS
VARIABLE STARS