Reflection-dominated nuclear X-ray emission in the early-type galaxy ESO 565--G019

TL;DR

This paper reports the discovery of a reflection-dominated, Compton-thick AGN in the early-type galaxy ESO 565--G019, highlighting its unique spectral features, variability, and potential implications for galaxy evolution and AGN growth.

Contribution

It presents the first confirmed case of a Compton-thick AGN in an early-type galaxy, expanding understanding of AGN obscuration in different host galaxy morphologies.

Findings

Spectral features characteristic of Compton-thick AGN detected

Long-term X-ray flux variability observed, linked to intrinsic AGN changes

Host galaxy shows signs of ongoing star formation and possible merger activity

Abstract

We present the discovery of a reflection-dominated active galactic nucleus (AGN) in the early-type radio-quiet galaxy ESO 565--G019 with Suzaku and Swift/BAT. The source X-ray spectrum below 10 keV is characteristic of other Compton-thick (CT) AGN, clearly showing an inverted continuum and prodigious fluorescence iron emission above ~3 keV. A Compton shoulder to the neutral Fe Kalpha line also appears to be present. There is evidence for long-term hard X-ray flux variability which we associate with changes in the intrinsic AGN power-law. The increasing sensitivity of ongoing and new hard X-ray surveys means that more such reflection-dominated AGN ought to be uncovered in the near future. ESO 565--G019 is hosted in an early-type galaxy whose morphology has been variously classified as either type E or type S0. Only about 20 bona fide CT-AGN have been identified in the local universe so far, and all exist in host galaxies with late Hubble types (S0 or later). CT columns of nuclear obscuring gas are uncommon in early-type galaxies in the local universe, so confirmation of the exact morphological class of ESO 565--G019 is important. Infrared photometry also shows the presence of large quantities of cool dust in the host, indicative of significant ongoing star-formation. ESO 565--G019 may be the first identified local example of minor-merger driven CT-AGN growth in an early-type host, or may be the result of interaction with its neighboring galaxy ESO 565--G018 in a wide pair.