Line-emitting clouds in the broad-line regions of active galactic nuclei - Geometry and phase functions
Abstract
For a spherical cloud photoionized by a distant point source, phase functions are derived to describe the anisotropy of the cloud's emission in a given spectral line. It is assumed that (1) the cloud is completely opaque to the line photons, which are produced at small optical depths; (2) the cloud surface emits the line orthotropically; (3) the line luminosity of an elementary surface area depends on the incident ionizing flux by a power law. The effect of the cloud geometry on the phase functions is discussed. The expressions obtained for the phase functions may be useful for investigating the structure of the regions in active galactic nuclei where the broad emission features are found.
- Publication:
-
Pisma v Astronomicheskii Zhurnal
- Pub Date:
- June 1985
- Bibcode:
- 1985PAZh...11..432S
- Keywords:
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- Active Galactic Nuclei;
- Computational Astrophysics;
- Emission Spectra;
- Geometrical Optics;
- Molecular Clouds;
- Spectral Line Width;
- Photoionization;
- Point Sources;
- Seyfert Galaxies;
- Astrophysics