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ABSTRACT As part of the mm-Wave Interferometric Survey of Dark Object Masses (WISDOM), we present a measurement of the mass of the supermassive black hole (SMBH) in the nearby early-type galaxy NGC 0383 (radio source 3C 031). This measurement is based on Atacama Large Millimeter/sub-millimeter Array (ALMA) cycle 4 and 5 observations of the 12CO (2–1) emission line with a spatial resolution of 58 × 32 pc2 (0. 18 arcsec × 0. 1 arcsec). This resolution, combined with a channel width of 10 km s−1, allows us to well resolve the radius of the black hole sphere of influence (measured as RSOI = 316 pc = 0. 98 arcsec), where we detect a clear Keplerian increase of the rotation velocities. NGC 0383 has a kinematically relaxed, smooth nuclear molecular gas disc with weak ring/spiral features. We forward model the ALMA data cube with the Kinematic Molecular Simulation (KinMS) tool and a Bayesian Markov Chain Monte Carlo method to measure an SMBH mass of (4. 2 ± 0. 7) × 109 M⊙, a F160W-band stellar mass-to-light ratio that varies from 2. 8 ± 0. 6 M⊙/L, \, ₅₁₆₀ₖ in the centre to 2. 4 ± 0. 3 M⊙/ L, \, ₅₁₆₀ₖ at the outer edge of the disc and a molecular gas velocity dispersion of 8. 3 ± 2. 1 km s−1 (all 3σ uncertainties). We also detect unresolved continuum emission across the full bandwidth, consistent with synchrotron emission from an active galactic nucleus. This work demonstrates that low-J CO emission can resolve gas very close to the SMBH (140\, 000 Schwarzschild radii) and hence that the molecular gas method is highly complimentary to megamaser observations, as it can probe the same emitting material.
North et al. (Mon,) studied this question.