The Nature of the Stable Soft X-ray Emissions in Several Types of Active Galactic Nuclei Observed by Suzaku

TL;DR

This study analyzes Suzaku X-ray data of five active galactic nuclei to identify a stable soft X-ray component responsible for the soft excess phenomenon, proposing a multi-zone Comptonization model as the most plausible explanation.

Contribution

It applies a spectral analysis method to multiple AGNs, revealing a stable soft X-ray component and proposing a multi-zone Comptonization model as a novel interpretation.

Findings

Identified a stable soft X-ray component below 3 keV in all objects.

The soft component explains the soft excess above a power-law fit.

Supported multi-zone Comptonization as a physically plausible model.

Abstract

To constrain the origin of the soft X-ray excess phenomenon seen in many active galactic nuclei, the intensity-correlated spectral analysis, developed by Noda et al. (2011b) for Markarian 509, was applied to wide-band (0.5-45 keV) Suzaku data of five representative objects with relatively weak reflection signature. They are the typical bare-nucleus type 1 Seyfert Fairall 9, the bright and typical type 1.5 Seyfert MCG-2-58-22, 3C382 which is one of the X-ray brightest broad line radio galaxies, the typical Seyfert-like radio loud quasar 4C+74.26, and the X-ray brightest radio quiet quasar MR2251-178. In all of them, soft X-ray intensities in energies below 3 keV were tightly correlated with that in 3-10 keV, but with significant positive offsets. These offsets, when calculated in finer energy bands, define a stable soft component in 0.5-3 keV. In each object, this component successfully explained the soft excess above a power-law fit. These components were interpreted in several alternative ways, including a thermal Comptonization component which is independent of the dominant power-law emission. This interpretation, considered physically most reasonable, is discussed from a viewpoint of Multi-Zone Comptonization, which was proposed for the black hole binary Cygnus X-1 (Makishima et al. 2008).