Black Hole Mass Estimates of Early-Type Galaxies NGC 4786, NGC 5193, and NGC 3245 Using ALMA CO Observations and Gas-Dynamical Models

Reliable mass measurements of central black holes are a necessary component in understanding black hole-host galaxy coevolution. Within the past few years, the Atacama Large Millimeter/submillimeter Array (ALMA) has provided some of the most precise black hole mass measurements. Our collaboration has obtained high angular resolution observations of rotating circumnuclear gas disks in more than 20 early-type galaxies, and we are carrying out dynamical modeling to determine the central black hole masses. Here, we present preliminary gas-dynamical modeling results for three early-type galaxies, NGC 4786, NGC 5193, and NGC 3245, based on ~0.3' CO(2-1) observations of each galaxy’s circumnuclear disk obtained in ALMA Cycles 3 and 5. Our models describe the rotation of a thin and dynamically cold disk, are fitted directly to the ALMA data cubes, and are optimized via chi-squared minimization. We highlight possible sources of uncertainty in our models and discuss their impact on the mass measurements’ error budget. This work will provide the first mass measurement of the central black holes in NGC 4786 and NGC 5193 and a second and independent mass measurement of the black hole in NGC 3245, which was previously measured using ionized gas kinematics observations obtained with the Hubble Space Telescope.