Searching for Compact Obscured Nuclei in Compton-thick Active Galactic Nuclei
Journal article, 2025
Compact obscured nuclei (CONs) are heavily obscured infrared cores that have been found in local (ultra-)luminous infrared galaxies. They show bright emission from vibrationally excited rotational transitions of HCN, known as HCN-vib, and are thought to harbor Compton-thick (CT, NH ≥ 1024 cm−2) active galactic nuclei (AGNs) or extreme compact starbursts. We explore the potential evolutionary link between CONs and CT-AGNs by searching for CONs in hard-X-ray-confirmed CT-AGNs 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-AGNs. We analyze these objects together with literature HCN-vib measurements of five additional hard-X-ray-confirmed CT-AGNs from the GOALS sample. We do not detect any CONs in this combined sample of nine CT-AGNs. We then explore a proposed evolutionary sequence in which CONs evolve into X-ray-detectable CT-AGNs 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-AGNs. While this could suggest that CT-AGNs are not universally linked to CONs, it could also be explained by a short duty cycle for molecular outflows.
Author
Makoto A. Johnstone
University of Virginia
Pontificia Universidad Catolica de Chile
G. Privon
College of Liberal Arts and Sciences
National Radio Astronomy Observatory
University of Virginia
Loreto Barcos-Munoz
University of Virginia
National Radio Astronomy Observatory
Aaron S. Evans
National Radio Astronomy Observatory
University of Virginia
Susanne Aalto
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
Lee Armus
California Institute of Technology (Caltech)
F. E. Bauer
Millennium Institute of Astrophysics
Pontificia Universidad Catolica de Chile
L. Blecha
College of Liberal Arts and Sciences
J. S. Gallagher III
Macalester College
University of Wisconsin Madison
Sabine König
Chalmers, Space, Earth and Environment, Onsala Space Observatory
C. Ricci
Diego Portales University
Beijing University of Technology
E. Treister
Pontificia Universidad Catolica de Chile
Cosima Eibensteiner
National Radio Astronomy Observatory
K.L. Emig
National Radio Astronomy Observatory
Kara N. Green
University of Virginia
Devaky Kunneriath
National Radio Astronomy Observatory
Jaya Nagarajan-Swenson
University of Virginia
Alejandro Saravia
University of Virginia
I. Yoon
National Radio Astronomy Observatory
Astrophysical Journal
0004-637X (ISSN) 1538-4357 (eISSN)
Vol. 985 2 259Subject Categories (SSIF 2025)
Atom and Molecular Physics and Optics
Astronomy, Astrophysics, and Cosmology
DOI
10.3847/1538-4357/adcecb