Dynamical mass measurements of supermassive black holes in local relic galaxies

Supermassive black holes (BHs) have been observed to correlate with host galaxy bulge properties, leading to a fundamental open question in galaxy evolution: do BHs and galaxies grow in lockstep, or does the growth of one precede that of the other? We have uncovered a sample of local compact galaxies that are thought to be local analogs/relics of z~2 quiescent galaxies. Previous stellar-dynamical modeling of three galaxies in this sample found BHs that were over-massive compared to the BH mass - bulge luminosity scaling relation, indicating BHs may build the majority of their mass before their host galaxies. Here, we present Atacama Large Millimeter/submillimeter Array (ALMA) CO(2-1) observations of the rotating circumnuclear disks in three more relic galaxies. We fit gas-dynamical models to the ALMA data, assuming the CO emission originates from a dynamically cold, thin disk, and determine Bayesian posteriors of parameters including BH mass. Finally, we place the relic galaxies on the BH mass - host galaxy scaling relations. Making more dynamical BH mass measurements for the sample of relic galaxies will significantly advance our understanding of BH - host galaxy co-evolution.

Speaker Bio: Jonathan Cohn (he/she/they) is an astronomy postdoc at Texas A&M University. He studies supermassive black holes and the relationships between black hole masses and host galaxy properties. In addition to science, she is passionate about transforming academia and society at large into a more equitable place. In their free time, Jonathan enjoys reading, creative writing, listening to music, playing tabletop games and RPGs, climbing, and hiking.