Discovery of Kiloparsec Extended Hard X-ray Continuum and Fe K alpha from the Compton Thick AGN ESO428-G014

TL;DR

This paper reports the discovery of kiloparsec-scale diffuse hard X-ray and Fe K alpha emission in the Compton Thick AGN ESO428-G014, revealing extended structures that impact our understanding of AGN spectra.

Contribution

It presents the first detection of extended hard X-ray and Fe K alpha emission on kiloparsec scales in a Compton Thick AGN, challenging existing models.

Findings

Extended hard X-ray emission accounts for ~24% of observed 3-8 keV flux.

The emission aligns with optical ionization cones and radio jets.

The extended component's luminosity can be explained by scattering or molecular clouds.

Abstract

We report the discovery of kpc-scale diffuse emission in both the hard continuum (3-6 keV) and in the Fe K alpha line in the Compton Thick (CT) Seyfert galaxy ESO428-G014. This extended hard component contains at least ~24% of the observed 3-8 keV emission, and follows the direction of the extended optical line emission (ionization cone) and radio jet. The extended hard component has ~0.5% of the intrinsic 2-10 keV luminosity within the bi-cones. A uniform scattering medium of density 1 cm-3 would produce this luminosity in a 1kpc path length in the bi-cones. Alternatively, higher column density molecular clouds in the disk of ESO428-G014 may be responsible for these components. The continuum may also be enhanced by the acceleration of charged particles in the radio jet. The steeper spectrum (Gamma ~1.7 +-0.4) of the hard continuum outside of the central 1.5" radius nuclear region suggests a contribution of scattered/fluorescent intrinsic Seyfert emission. Ultrafast nuclear outflows cannot explain the extended F K alpha emission. This discovery suggests that we may need to revise the picture at the base of our interpretation of CT AGN spectra.