Deep Chandra Observations of ESO 428-G014: II. Spectral Properties and Morphology of the Large-Scale Extended X-ray Emission

TL;DR

This study uses deep Chandra observations to analyze the spectral and spatial properties of large-scale X-ray emission in the Compton thick AGN ESO 428-G014, revealing complex ionization, scattering, and extended emission features.

Contribution

It provides detailed spectral and morphological analysis of the diffuse X-ray emission, highlighting the role of molecular clouds and the extent of emission beyond the obscuring torus.

Findings

Diffuse emission is more extended at lower energies (<3 keV).

Cross-cone emission is significantly extended, indicating partial transmission through the torus.

Soft diffuse emission likely from hot ISM, with luminosity ~5×10^38 erg s^-1.

Abstract

We present a deep Chandra spectral and spatial study of the kpc-scale diffuse X-ray emission of the Compton thick (CT) AGN ESO428-G014. The entire spectrum is best fit with composite photoionization + thermal models. The diffuse emission is more extended at the lower energies (<3 keV). The smaller extent of the hard continuum and Fe K{\alpha} profiles imply that the optically thicker clouds responsible for this scattering may be relatively more prevalent closer to the nucleus. These clouds must not prevent soft ionizing X-rays from the AGN escaping to larger radii, in order to have photoionized ISM at larger radii. This suggests that at smaller radii there may be a larger population of molecular clouds to scatter the hard X-rays, as in the Milky Way. The diffuse emission is also significantly extended in the cross-cone direction, where the AGN emission would be mostly obscured by the torus in the standard AGN model. Our results suggest that the transmission of the obscuring region in the cross-cone direction is ~10% than in the cone-direction. In the 0.3-1.5 keV band, the ratio of cross-cone to cone photons increases to ~84\%, suggesting an additional soft diffuse emission component, disjoint from the AGN. This could be due to hot ISM trapped in the potential of the galaxy. The luminosity of this component ~5 10^38 erg s^-1 is roughly consistent with the thermal component suggested by the spectral fits in the 170-900 pc annulus.