Extended hard X-ray emission in highly obscured AGN

TL;DR

This study investigates extended hard X-ray emission in heavily obscured AGN, revealing that such emission is common and more extended in Compton-thick AGN, with implications for understanding AGN structure and feedback.

Contribution

It provides the first spatial analysis of non-CT heavily obscured AGN, comparing their extended X-ray emission to CT AGN, and discusses implications for AGN torus models and feedback mechanisms.

Findings

Extended hard X-ray emission detected in 3 of 5 AGN at >3σ

CT AGN tend to have more extended hard X-ray emission than non-CT AGN

Extended emission accounts for 8-20% of total hard X-ray flux

Abstract

Kilo-parsec scale hard ($>$ 3 keV) X-ray continuum and fluorescent Fe K$\alpha$ line emission has been recently discovered in nearby Compton-thick (CT) active galactic nuclei (AGN), which opens new opportunities to improve AGN torus modeling and investigate how the central supermassive black hole interacts with and impacts the host galaxy. Following a pilot Chandra survey of nearby CT AGN, we present in this paper the Chandra spatial analysis results of five uniformly selected non-CT but still heavily obscured AGN to investigate the extended hard X-ray emission by measuring the excess emission counts, excess fractions, and physical scales. Three of them show extended emission in the 3.0-7.0 keV band detected at $>$ 3$\sigma$ above the Chandra PSF with total excess fractions ranging from $\sim$8% - 20%. The extent of the hard emission ranges from at least $\sim$250 pc to 1.1 kpc in radius. We compare these new sources with CT AGN and find that CT AGN appear to be more extended in the hard band than the non-CT AGN. Similar to CT AGN, the amounts of extended hard X-ray emission relative to the total emission of these obscured AGN are not negligible. Together with other extended hard X-ray detected AGN in the literature, we further explore potential correlations between the extended hard X-ray component and AGN parameters. We also discuss the implications for torus modeling and AGN feedback. Considering potential contributions from X-ray binaries (XRBs) to the extended emission, we do not see strong XRB contamination in the overall sample.