Soft X-Ray Absorption by Fe to Fe in Active Galactic Nuclei
نویسندگان
چکیده
A full set of calculations is presented for inner-shell n = 2 to 3 photoexcitation of the 16 iron charge states: Fe (Fe I) through Fe (Fe XVI). The blend of the numerous absorption lines arising from these excitations (mainly 2p 3d) forms an unresolved transition array (UTA), which has been recently identified as a prominent feature between 16 17 Å in the soft X-ray spectra of active galactic nuclei (AGN). Despite the blending within charge-states, the ample separation between the individual-ion features enables precise diagnostics of the ionization range in the absorbing medium. Column density and turbulent velocity diagnostics are also possible, albeit to a lesser accuracy. An abbreviated set of atomic parameters useful for modeling the Fe 2p 3d UTA is given. It is shown that the effects of accompanying photoexcitation to higher levels (n ≥ 4), as well as the associated photoionization edges, may also be relevant to AGN spectra. Subject headings: atomic data — atomic processes — line: formation — galaxies: active — galaxies: nuclei — X-rays: galaxies
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