Article ID Journal Published Year Pages File Type
1780083 New Astronomy Reviews 2009 7 Pages PDF
Abstract

Here we discuss the physical conditions in the emission line regions (ELR) of active galactic nuclei (AGN), with the special emphasize on the unresolved problems, e.g. the stratification of the Broad Line Region (BLR) or the failure of the photoionization to explain the strong observed optical Fe II emission. We use here different line fluxes in order to probe the properties of the ELR, such as the hydrogen Balmer lines (HαHα to HεHε), the helium lines from two subsequent ionization levels (He IIλ4686 and He Iλ5876) and the strongest Fe II lines in the wavelength interval λλ4400–5400Å. We found that the hydrogen Balmer and helium lines can be used for the estimates of the physical parameters of the BLR, and we show that the Fe II emission is mostly emitted from an intermediate line region (ILR), that is located further away from the central continuum source than the BLR.

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Physical Sciences and Engineering Physics and Astronomy Astronomy and Astrophysics
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