Rest-frame stacking of 2XMM catalog sources : Properties of the Fe Kalpha line

TL;DR

This study analyzes the average Fe K emission in a large, diverse sample of AGNs across a wide redshift range using rest-frame stacking, revealing a composite line profile with narrow and broad components.

Contribution

It introduces two independent rest-frame stacking methods to characterize Fe K emission in AGNs, covering a broad redshift range and high counts, with detailed simulations to validate the approach.

Findings

Average Fe K line profile includes narrow and broad components.

Equivalent widths are approximately 30 eV for narrow and 100 eV for broad lines.

Results suggest complex Fe K emission features in AGNs across redshifts.

Abstract

The aim of this work is to characterize the average Fe K emission properties of active galactic nuclei (AGNs) in the source rest-frame. We selected a sample of 248 AGNs from the 2XMM catalog, covering a wide redshift range 0 < z < 5 and with the EPIC-PN net 2-10 keV rest-frame counts >=200 and power law photon indices in the range 1.5-2.2. We employed two fully independent rest-frame stacking procedures to compute the mean Fe K profile. The counting statistics for the integrated spectrum is comparable to the one available for the best studied local Seyferts. To identify the artifacts possibly introduced by the stacking procedure, we have carried out simulations. We report that the average Fe K line profile in our sample is best represented by a combination of a narrow and a broad line. The equivalent widths of the narrow and broad (parametrized with a diskline) components are ~30 eV and ~100 eV, respectively. We also discuss the results of more complex fits and the implications of the adopted continuum modeling on the broad line parameters and its detection significance.