TPHO: a time-dependent photoionisation model for AGN outflows

Abstract

Outflows in active galactic nuclei (AGN) are considered a promising candidate for driving AGN feedback at large scales. However, without information on the density of these outflows, we cannot determine how much kinetic power they are imparting to the surrounding medium. Monitoring the response of the ionisation state of the absorbing outflows to changes in the ionising continuum provides the recombination timescale of the outflow, which is a function of the electron density. We have developed a new self-consistent time-dependent photoionisation model, TPHO, enabling the measurement of the plasma density through time-resolved X-ray spectroscopy. The algorithm solves the full-time-dependent energy and ionisation balance equations in a self-consistent fashion for all the ionic species. The model can therefore reproduce the time-dependent absorption spectrum of ionized outflows responding to changes in the ionizing radiation of the AGN. We find that when the ionised gas is in a non-equilibrium state its transmitted spectra are not accurately reproduced by standard photoionisation models. Our simulations with the current X-ray grating observations show that the spectral features identified as a multiple-components warm absorber, might be in fact features of a time-changing warm absorber and not distinctive components. The TPHO model facilitates accurate photoionisation modelling in the presence of a variable ionising source, thus providing constraints on the density and in turn the location of the AGN outflows. Ascertaining these two parameters will provide important insight into the role and impact of ionised outflows in AGN feedback.

19 pages, 13 figures, accepted for publication by Apj on 07-Oct-22

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Cited by in corpus (8)

• Scientific Objectives of the Hot Universe Baryon Surveyor (HUBS) Mission
• A systematic study of the ultra-fast outflow responses to luminosity variations in active galactic nuclei
• Time-dependent photoionization spectroscopy of the Seyfert galaxy NGC 3783
• Time Evolving Photo Ionisation Device (TEPID): a novel code for out-of-equilibrium gas ionisation
• Density calculations of NGC 3783 warm absorbers using a time-dependent photoionization model
• A failed wind candidate in NGC 3783 from the 2001 year campaign with Chandra/HETGS
• Discovery of the Asymmetric Effect in the Response of Photoionization Gas
• Probing extreme black-hole outflows on short timescales via high spectral-resolution X-ray imagers