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arXiv · 2504.15248

Searching for Compact Obscured Nuclei in Compton Thick AGN

Makoto A. Johnstone·George C. Privon·Loreto Barcos-Munoz·A. S. Evans·S. Aalto·Lee Armus·Franz E. Bauer·L. Blecha·J. S. Gallagher·S. König·Claudio Ricci·Ezequiel Treister·Cosima Eibensteiner·Kimberly L. Emig·Kara N. Green·Devaky Kunneriath·Jaya Nagarajan-Swenson·Alejandro Saravia·Ilsang Yoon
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Abstract

Compact Obscured Nuclei (CONs) are heavily obscured infrared cores that have been found in local (ultra)luminous infrared galaxies (U/LIRGs). They show bright emission from vibrationally excited rotational transitions of HCN, known as HCN-vib, and are thought to harbor Compton Thick (CT, $N_{\text{H}} \geq 10^{24}$ cm$^{-2}$) active galactic nuclei (AGN) or extreme compact starbursts. We explore the potential evolutionary link between CONs and CT AGN by searching for CONs in hard X-ray-confirmed CT AGN from the Great Observatories All-sky LIRG Survey (GOALS). Here, we present new Atacama Large Millimeter/submillimeter Array Band 6 observations that targeted HCN-vib emission in four hard X-ray-confirmed CT AGN. We analyze these objects together with literature HCN-vib measurements of five additional hard X-ray-confirmed CT AGN from the GOALS sample. We do not detect any CONs in this combined sample of nine CT AGN. We then explore a proposed evolutionary sequence in which CONs evolve into X-ray-detectable CT AGN once outflows and feedback reduce the column densities of the enshrouding gas. We find, however, no evidence of well-developed dense molecular outflows in the observed CT AGN. While this could suggest that CT AGN are not universally linked to CONs, it could also be explained by a short duty cycle for molecular outflows.

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Makoto A. Johnstone, George C. Privon, Loreto Barcos-Munoz, A. S. Evans, S. Aalto, Lee Armus, Franz E. Bauer, L. Blecha, J. S. Gallagher, S. König, Claudio Ricci, Ezequiel Treister, Cosima Eibensteiner, Kimberly L. Emig, Kara N. Green, Devaky Kunneriath, Jaya Nagarajan-Swenson, Alejandro Saravia, Ilsang Yoon. 2025-04-26. Searching for Compact Obscured Nuclei in Compton Thick AGN. https://arxiv.org/abs/2504.15248

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