Fast ionized X‐ray absorbers in AGNs

Abstract

AbstractWe investigate the physics of the X‐ray ionized absorbers often identified as warm absorbers (WAs) and ultra‐fast outflows (UFOs) in Seyfert AGNs from spectroscopic studies in the context of magnetically‐driven accretion‐disk wind scenario. Launched and accelerated by the action of a global magnetic field anchored to an underlying accretion disk around a black hole, outflowing plasma is irradiated and ionized by an AGN radiation field characterized by its spectral energy density (SED). By numerically solving the Grad‐Shafranov equation in the magnetohydrodynamic (MHD) framework, the physical property of the magnetized disk‐wind is determined by a wind parameter set, which is then incorporated into radiative transfer calculations with xstar photoionization code under heating‐cooling equilibrium state to compute the absorber's properties such as column density NH, line‐of‐sight (LoS) velocity v, ionization parameter ς, among others. Assuming that the wind density scales as n ∝ r–1, we calculate theoretical absorption measure distribution (AMD) for various ions seen in AGNs as well as line spectra especially for the Fe Kα absorption feature by focusing on a bright quasar PG 1211+143 as a case study and show the model's plausibility. In this note we demonstrate that the proposed MHD‐driven disk‐wind scenario is not only consistent with the observed X‐ray data, but also help better constrain the underlying nature of the AGN environment in a close proximity to a central engine. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)