Resonant absorption in the active galactic nucleus spectra emerging from photoionized gas: Differences between steep and flat ionizing continua

We present photoionization models accounting for both photoelectric and res onant absorption. Resonance absorption lines from C, O, Ne, Mg, Si, S, and Fe between 0.1 and 10 keV are treated. In particular we consider the comple x of almost 60 strong Fe L absorption lines around 1 keV. We calculate prof iles, intensities, and equivalent widths of each line, considering both Dop pler and natural broadening mechanisms. Doppler broadening includes a term accounting for turbulence of the gas along the line of sight. We computed s pectra transmitted by gas illuminated by drastically different ionizing con tinua and compared them to spectra observed in flat X-ray spectrum, broad o ptical emission-line type active galactic nuclei (AGNs), and steep X-ray sp ectrum, narrow optical emission-line type AGNs. We show that the similar to 1 keV absorption feature observed in moderate-resolution X-ray spectra of several narrow-line Seyfert 1 galaxies can be explained by photoionization models, taking into account resonance absorption, without requiring relativ istic outflowing velocities of the gas, if the physical properties of these absorbers are close to those found in Bat X-ray spectrum Seyfert 1 galaxie s. We finally present simulations of the spectra emerging from gas illumina ted by both steep and flat ionizing continua, as seen by the AXAF high-ener gy transmission gratings and the baseline Constellation-X calorimeter. We d iscuss briefly the relevant physics that can be investigated with these ins truments.