Constraining Nuclear Molecular Gas Content with High-resolution CO Imaging of GOALS Galaxies

February 2026 • 2026ApJ...998..343A

Authors • Agostino, James • Medling, Anne M. • Barcos-Muñoz, Loreto • U, Vivian • Rodríguez Vásquez, Mynor • Privon, George C. • Cicone, Claudia • Armus, Lee • Moreno, Jorge • Ricci, Claudio • Song, Yiqing • Hayward, Christopher C. • Alatalo, Katherine • Sanders, David B.

Abstract • We present measurements of the cool molecular gas mass around the nuclei of two gas-rich mergers, III Zw 035 and IRAS F01364−1042, whose enclosed masses (M_enc) within the central 40─80 pc would be overmassive if attributed entirely to the supermassive black hole (SMBH) mass and compared to SMBH─galaxy scaling relations. Our gas mass measurements are derived from Atacama Large Millimeter/submillimeter Array (ALMA) Band 6 long-baseline observations of CO(J = 2─1) and 230 GHz continuum emission at 14─20 pc resolution, which probes below the resolving limit of the previous black hole mass measurements. Subtracting molecular gas mass from these enclosed masses is not enough to reconcile with black hole─galaxy relationships, but independently measuring M_enc using the cold CO(2─1) gas does shift the black holes down to their expected values. Still, these ALMA data reveal respective molecular gas masses of ∼3 × 10⁷ to ∼6 × 10⁸ M_⊙ within 70 pc of these black holes, which could challenge some black hole accretion models that assume nuclear gas like this has no angular momentum.

Links

• ELECTR https://doi.org/10.3847/1538-4357/ae3c04
• PREPRINT http://arxiv.org/abs/2601.16057