Formation of Fe II lines in AGN
Abstract
Up to now, photoionization models of the broad-line region of quasars fail to explain the strength of low-ionization lines; in particular, Fe II lines are too weak compared to H-beta. Using a code mainly designed to study low ionized and optically thick medium, the radiation transfer in a nonphotoionized homogeneous cloud has been studied in order to outline the physical conditions required to explain the observed Fe II intensities. The results of the computations are compared to the published line ratios of about 30 well-observed AGN. It is shown that the 'Fe II/H-beta problem' is not easily solved as regards the strong UV Fe II emitters, while low-temperature clouds provide Fe II opt/H-beta in agreement with observations.
- Publication:
-
IAU Colloq. 94: Physics of Formation of FE II Lines Outside LTE
- Pub Date:
- 1988
- DOI:
- 10.1007/978-94-009-4023-9_30
- Bibcode:
- 1988ASSL..138..259J
- Keywords:
-
- Active Galactic Nuclei;
- Iron;
- Line Spectra;
- Photoionization;
- Ultraviolet Spectra;
- Astronomical Models;
- H Lines;
- Space Density;
- Visible Spectrum;
- Astrophysics