Observational model of the ionized gas in Seyfert and radio-galaxy nuclei

Journal Article · Wed Feb 01 00:00:00 EST 1978 · Proc. Natl. Acad. Sci. U.S.A.; (United States)

DOI:https://doi.org/10.1073/pnas.75.2.540· OSTI ID:6753449

Osterbrock, D E

Equivalent widths of the total emission-line H..beta.. in Seyfert 1, Seyfert 2, and intermediate-type Seyfert galaxies, expressed in terms of the featureless continuum, all have approximately the same frequency distribution. This suggests that the energy-input mechanism to both the narrow-line, low density gas and the broad-line, high density gas is photoionization by the featureless continuum. The reason for the weakness of the narrow emission lines in extreme Seyfert 1 galaxies is then the absorption of most of the ionizing photons in the dense gas near the central source. The statistics of line widths can be fitted by a model in which the dense gas has typical rotational velocity 5000 km/sec and typical turbulent velocity 2000 km/sec. A model is proposed in which the dense gas forms a rotating, turbulent disk with dimension approximately equal to 0.1 pc and height/diameter approximately equal to 2/5. Seyfert 2 galaxies are objects with little dense gas, and intermediate-type Seyfert galaxies are objects in which the dense gas is optically thin to ionizing radiation at least along the poles. Most radio galaxies have strong narrow emission lines, suggesting that escape of radio plasma can only occur where some ionizing photons can also escape from the dense gas. Other predictions, implications, and tests of this model are discussed.

• Research Organization: Univ. of Minnesota, Minneapolis, MN (United States)
• OSTI ID: 6753449
• Journal Information: Proc. Natl. Acad. Sci. U.S.A.; (United States), Vol. 75:2
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
RADIO GALAXIES
IONIZED GASES
SEYFERT GALAXIES
ABSORPTION
DIMENSIONS
DISTRIBUTION
EMISSION SPECTRA
ENERGY
FREQUENCY DEPENDENCE
IONIZING RADIATIONS
KINETICS
LINE WIDTHS
PHOTOIONIZATION
PHOTONS
PLASMA
ROTATION
STATISTICS
STRUCTURAL MODELS
TURBULENCE
VELOCITY
COSMIC RADIO SOURCES
ELEMENTARY PARTICLES
FLUIDS
GALAXIES
GASES
IONIZATION
MASSLESS PARTICLES
MATHEMATICS
MOTION
RADIATIONS
SPECTRA
640103* - Astrophysics & Cosmology- Quasi-Stellar
Radio
& X-Ray Sources- (-1987)
640105 - Astrophysics & Cosmology- Galaxies