X-Ray Absorption Analysis of MCG-6-30-15: Discerning Three Kinematic Systems
Abstract
By analyzing the X-ray spectrum of MCG-6-30-15 obtained with the HETG spectrometer on board the Chandra Observatory, we identify three kinematically distinct absorption systems; two outflow components intrinsic to MCG-6-30-15, and one local at z = 0. The slow outflow at -100 +/- 50 km s-1 has a large range of ionization manifested by absorption from 24 different charge states of Fe, which enables a detailed reconstruction of the absorption measure distribution (AMD). This AMD spans five orders of magnitude in ionization parameter: -1.5 < log xi < 3.5 (cgs units), with a total column density of NH = (5.3 +/- 0.7) x 1021 cm-2. The fast outflow at -1900 +/- 150 km s-1 has a well defined ionization parameter with log xi = 3.82 +/- 0.03 (cgs units) and column density NH = 8.1 +/- 0.7 x 1022 cm-2. Assuming this component is a thin, uniform, spherical shell, it can be estimated to lie within 11 light days of the center. The third component, most clearly detected in the lower oxygen charge states O+1 - O+6, has been confused in the past with the fast outflow, but is identified here with local gas z = 0 and a total column density NH of a few 1020 cm-2. Finally, we exploit the excellent spectral resolution of the HETGS and use the present spectrum to determine the rest-frame wavelengths of oxygen inner-shell lines that were previously uncertain.