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 (Menc) within the central 40-80 pc would be overmassive if attributed entirely to the supermassive black hole mass (SMBH) 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 BH-galaxy relationships, but independently measuring Menc 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.
@article{arxiv.2601.16057,
title = {Constraining Nuclear Molecular Gas Content with High-resolution CO Imaging of GOALS Galaxies},
author = {James Agostino and Anne M. Medling and Loreto Barcos-Muñoz and Vivian U and Mynor Rodríguez Vásquez and George C. Privon and Claudia Cicone and Lee Armus and Jorge Moreno and Claudio Ricci and Yiqing Song and Christopher C. Hayward and Katherine Alatalo and David B. Sanders},
journal= {arXiv preprint arXiv:2601.16057},
year = {2026}
}