# WISDOM Project - I: Black Hole Mass Measurement Using Molecular Gas Kinematics in NGC 3665

## TL;DR

This study measures the supermassive black hole mass in galaxy NGC 3665 using molecular gas kinematics from millimeter-wave observations, providing precise estimates and confirming consistency with galaxy property correlations.

## Contribution

First to model SMBH mass in NGC 3665 using 3D molecular gas kinematics with high-resolution millimeter observations.

## Key findings

- SMBH mass estimated at approximately 5.75 x 10^8 solar masses.
- Molecular gas kinematics consistent with previous methods and galaxy property correlations.
- Systematic uncertainties quantified for SMBH mass and stellar mass-to-light ratio.

## Abstract

As a part of the mm-Wave Interferometric Survey of Dark Object Masses (WISDOM) project, we present an estimate of the mass of the supermassive black hole (SMBH) in the nearby fast-rotator early-type galaxy NGC 3665. We obtained Combined Array for Research in Millimeter Astronomy (CARMA) B and C array observations of the $^{12}$CO$(J=2-1)$ emission line with a combined angular resolution of $0".59$. We analysed and modelled the three-dimensional molecular gas kinematics, obtaining a best-fit SMBH mass $M_{\rm BH}=5.75^{+1.49}_{-1.18} \times 10^{8}$ $M_{\odot}$, a mass-to-light ratio at $H$-band $(M/L)_{H}=1.45\pm0.04$ $(M/L)_{\odot, H}$, and other parameters describing the geometry of the molecular gas disc (statistical errors, all at $3\sigma$ confidence). We estimate the systematic uncertainties on the stellar $M/L$ to be $\approx0.2$ $(M/L)_{\odot, H}$, and on the SMBH mass to be $\approx0.4\times10^{8}$ $M_{\odot}$. The measured SMBH mass is consistent with that estimated from the latest correlations with galaxy properties. Following our older works, we also analysed and modelled the kinematics using only the major-axis position-velocity diagram, and conclude that the two methods are consistent.