The soft X-ray polarization in obscured AGN

TL;DR

This paper investigates the polarization of soft X-ray emission in obscured AGN, proposing that the continuum may be Thomson scattered nuclear radiation, which should be highly polarized, based on geometric modeling.

Contribution

It introduces a model linking soft X-ray polarization to Thomson scattering in the NLR, providing predictions for polarization levels in obscured AGN.

Findings

Predicted high polarization levels for the scattered continuum.

Quantified the fraction of reflected continuum in bright obscured AGN.

Linked polarization signatures to the geometry of the NLR.

Abstract

The soft X-ray emission in obscured active galactic nuclei (AGN) is dominated by emission lines, produced in a gas photoionized by the nuclear continuum and likely spatially coincident with the optical narrow line region (NLR). However, a fraction of the observed soft X-ray flux appears like a featureless power law continuum. If the continuum underlying the soft X-ray emission lines is due to Thomson scattering of the nuclear radiation, it should be very highly polarized. We calculated the expected amount of polarization assuming a simple conical geometry for the NLR, combining these results with the observed fraction of the reflected continuum in bright obscured AGN.