Excitation of MG II and Fe II lines in quasars and Seyfert galaxies
Abstract
Some of the most extensively observed, but least understood, features in the spectra of quasars and Seyfert galaxies are strong and broad lines of Fe II. Most attempts to explain the excitation of these lines have been restricted to the general framework of photoionization and assumed uniform density and temperature across the line formation zone. The present investigation incorporates the solution of the statistical equilibrium equations for the Fe(+) atom into a more nearly realistic photoionization model in an attempt to gain deeper insight into the line formation. The related question of the excitation of Mg II is also investigated. The observational situation and the proposed excitation mechanisms are summarized. A detailed discussion is presented of the physical processes and gasdynamics that are likely to affect the line strengths. The calculations involved are described, and the implications for quasar models are discussed.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 1980
- DOI:
- 10.1086/157757
- Bibcode:
- 1980ApJ...236..406N
- Keywords:
-
- Iron;
- Line Spectra;
- Magnesium;
- Quasars;
- Seyfert Galaxies;
- Stellar Spectra;
- Abundance;
- Atomic Excitations;
- Equilibrium Equations;
- Mass Distribution;
- Optical Thickness;
- Photoionization;
- Stellar Models;
- Ultraviolet Astronomy;
- Astrophysics