Multi-wavelength campaign on NGC7469 II. Column densities and variability in the X-ray spectrum

TL;DR

This study analyzes X-ray observations of NGC7469 over ten years to determine the properties, variability, and impact of ionized outflows, providing insights into their location and role in galactic feedback.

Contribution

It introduces an individual-ion spectral fitting approach to assess outflow variability and constrains the outflow's distance and kinetic power, advancing understanding of AGN feedback mechanisms.

Findings

No significant column density variability over 10 years.

Outflows are located at least 12-31 parsecs from the nucleus.

Kinetic power of outflows is between 0.4% and 60% of Eddington luminosity.

Abstract

We investigate the ionic column density variability of the ionized outflows associated with NGC$\sim$7469, to estimate their location and power. This could allow a better understanding of galactic feedback of AGNs to their host galaxies. Analysis of seven XMM-Newton grating observations from 2015 is reported. We use an individual-ion spectral fitting approach, and compare different epochs to accurately determine variability on time-scales of years, months, and days. We find no significant column density variability in a 10 year period implying that the outflow is far from the ionizing source. The implied lower bound on the ionization equilibrium time, 10 years, constrains the lower limit on the distance to be at least 12 pc, and up to 31 pc, much less but consistent with the 1 kpc wide starburst ring. The ionization distribution of column density is reconstructed from measured column densities, nicely matching results of two 2004 observations, with one large high ionization parameter ($\xi$) component at $2<\log \xi<3.5$, and one at $0.5<\log \xi<1$ in cgs units. The strong dependence of the expression for kinetic power, $\propto1/\xi$, hampers tight constraints on the feedback mechanism of outflows with a large range in ionization parameter, which is often observed and indicates a non-conical outflow. The kinetic power of the outflow is estimated here to be within 0.4 and 60 \% of the Eddington luminosity, depending on the ion used to estimate $\xi$.