The Soft X‐Ray Spectrum of Scattering‐dominated Active Galactic Nuclei

This paper discusses the properties of scattering--dominated active galacticnuclei (AGN). We define these to be AGN for which the direct line-of-sight tothe continuum source is obscured by Compton-thick material. The aim is toconstruct, for the first time, a model consistent with X-ray line luminosities,line ratios and various luminosity indicators. The ASCA spectra of six suchsources show several X-ray lines that can be reliably measured, mostly due tohighly ionized magnesium, silicon sulphur and iron. These enable us toinvestigate the physical conditions of the scattering material. The sourcesshow evidence of He-like and H-like iron lines that are likely to be producedin hot (T approx 10^6 K) photoionized gas. By measuring the EW of the lines,and by constructing a diagnostic line-ratio diagram, we demonstrate that thesilicon and magnesium lines are produced by the same gas emitting the highlyionized iron lines. The properties of this gas are rather different from theproperties of warm absorbers in type I AGN. Neutral 6.4 keV iron lines are alsodetected, originating in a different component which can be either Compton-thinor Compton-thick. The best measured iron lines suggest an enhancement ofn_{Fe}/n_H by a factor approx 2 compared to solar, in both the hot and coolCompton-thin components. We further show that in four of the sources, the FeKalpha(6.4keV)/Hbeta (lambda 4861Ang) line ratio is consistent with thatpredicted for typical narrow line region clouds, and the reddening correctedHbeta is known, provided the column density is larger than approx10^{22.5}/cm^2, alpha_{ox} is smaller than 1.3. For some sources, this is aviable alternative to the commonly assumed Compton thick medium as the originof the 6.4 keV iron line.Comment: Accepted for publication in ApJ. LaTeX, 30 pages (including 8 figs and 2 tables