X-ray outflows of active galactic nuclei warm absorbers: A 900 ks Chandra simulated spectrum

TL;DR

This paper presents a method to analyze X-ray spectra of active galactic nuclei warm absorbers, estimating gas density and location by comparing observed and theoretical absorption line properties.

Contribution

It introduces the XLINE-ID procedure, combining photoionisation models and theoretical line curves to determine the properties of AGN warm absorbers from simulated spectra.

Findings

Successful estimation of gas density and location of warm absorbers

Effective identification of ionization states and column densities

Validation of the XLINE-ID method on simulated data

Abstract

We report on the performance of the statistical, X-ray absorption lines identification procedure XLINE-ID. As illustration, it is used to estimate the time averaged gas density $n_H(r)$ of a representative AGN's warm absorber ($T\approx 10^5$~K) X-ray simulated spectrum. The method relies on three key ingredients: (1) a well established emission continuum level; (2) a robust grid of photoionisation models spanning several orders of magnitude in gas density ($n_H$), plasma column density ($N_H$), and in ionization states; (3) theoretical curves of growth for a large set of atomic lines. By comparing theoretical and observed equivalent widths of a large set of lines, spanning highly ionized charge states from O, Ne, Mg, Si, S, Ar, and the Fe L-shell and K-shell, we are able to infer the location of the X-ray warm absorber.