NOEMA Detection of Circumnuclear Molecular Gas in X-Ray Weak Dual Active Galactic Nuclei: No Evidence for Heavy Obscuration

Dual active galactic nuclei (AGNs), which are the manifestation of two actively accreting supermassive black holes (SMBHs) hosted by a pair of merging galaxies, are a unique laboratory for studying the physics of SMBH feeding and feedback during an indispensable stage of galaxy evolution. In this work, we present NOEMA CO(2-1) observations of seven kiloparsec-scale dual-AGN candidates drawn from a recent Chandra survey of low redshift, optically classified AGN pairs. These systems are selected because they show unexpectedly low 2-10 keV X-ray luminosities for their small physical separations signifying an intermediate-to-late stage of merger. Circumnuclear molecular gas traced by the CO(2-1) emission is significantly detected in six of the seven pairs and 10 of the 14 nuclei, with an estimated mass ranging between (0.2-21) × 10⁹ M _⊙. The primary nuclei, i.e., the ones with the higher stellar velocity dispersion, tend to have a higher molecular gas mass than the secondary. Most CO-detected nuclei show a compact morphology, with a velocity field consistent with a kiloparsec-scale rotating structure. The inferred hydrogen column densities range between 5 × 10²¹-2 × 10²³ cm⁻², but mostly at a few times 10²² cm⁻², in broad agreement with those derived from X-ray spectral analysis. Together with the relatively weak mid-infrared emission, the moderate column density argues against the prevalence of heavily obscured, intrinsically luminous AGNs in these seven systems, but favors a feedback scenario in which AGN activity triggered by a recent pericentric passage of the galaxy pair can expel circumnuclear gas and suppress further SMBH accretion.