Supermassive black hole (SMBH) masses can be measured using molecular gas kinematics. Here we present high angular resolution ($0.12$ arcsec or $\approx11$ pc) Atacama Large Millimeter/submillimeter Array observations of the $^{ 12}$CO(2-1) line emission of the early-type galaxy NGC 1387. The observations reveal a face-on, regularly-rotating central molecular gas disc with a diameter of $\approx18$ arcsec ($\approx1.7$ kpc) and a central depression slightly larger than the SMBH sphere of influence. We forward model the CO data cube in a Bayesian framework with the \textsc{ Kinematic Molecular Simulation} code, and use \textit{ Hubble Space Telescope} data to constrain the stellar gravitational potential contribution to the molecular gas kinematics. We infer a SMBH mass of $1.10^{ +1.71}_{ -0.95}[\text{ stat},3\sigma]^{ +2.45}_{ -1.09}[\text{ sys}]\times10^8$ M$_\odot$ and a F160W-filter stellar mass-to-light ratio of $0.90^{ +0.44}_{ -0.35}[\text{ stat}, 3\sigma]^{ +0.46}_{ -0.36}[\text{ sys}]$ M$_\odot$/L$_{ \odot,\text{ F160W}}$. This SMBH mass is consistent with the SMBH mass -- stellar velocity dispersion relation.
Categories: astro-ph.GA