Observable Properties of X-ray Heated Winds in AGN: Warm Reflectors and Warm Absorbers

Abstract

When an AGN is obscured, the warm reflecting gas nearby can be seen by a combination of bremsstrahlung, intrinsic line emission, and reflection of the nuclear continuum, both by electron scattering and by resonance line scattering. Resonance lines, due both to intrinsic emission and scattering, are particularly prominent in the soft X-ray band. When our line of sight to the nucleus is not obscured, the dominant effect is absorption. In the soft X-ray band, ionization edges of highly ionized species and resonance lines contribute comparably to the opacity; in the ultraviolet, the gas is almost transparent except for a small number of resonance lines. We identify the "warm absorbers" seen in many AGN X-ray spectra with this gas, but argue that most of the UV absorption lines seen must be due to a small amount of more weakly ionized gas which is embedded in the main body of the warm, reflecting gas. Because the ionization equilibration timescales of some ions may be as long as the variability timescales in AGN, the ionic abundances indicated by the transmission spectra may not be well-described by ionization equilibrium.