WISDOM Project -- XIII. Feeding molecular gas to the supermassive black hole in the starburst AGN-host galaxy Fairall 49

TL;DR

This study uses high-resolution ALMA CO observations to measure the supermassive black hole mass, gas dynamics, and inflow rates in the galaxy Fairall 49, revealing insights into SMBH growth and molecular gas properties.

Contribution

First application of WISDOM survey techniques to an AGN-host galaxy, providing SMBH mass, gas inflow rates, and X_CO factor estimates with high-resolution molecular gas data.

Findings

SMBH mass is approximately 1.6 x 10^8 solar masses.

The molecular gas disk shows radial inflow with weak feedback effects.

The inferred gas inflow rate can reach up to 5 solar masses per year.

Abstract

The mm-Wave Interferometric Survey of Dark Object Masses (WISDOM) is probing supermassive black holes (SMBHs) in galaxies across the Hubble sequence via molecular gas dynamics. We present the first WISDOM study of a luminous infrared galaxy with an active galactic nuclei (AGN): Fairall 49. We use new ALMA observations of the CO(2-1) line with a spatial resolution of about 80 pc together with ancillary HST imaging. We reach the following results: (1) The CO kinematics are well described by a regularly rotating gas disk with a radial inflow motion, suggesting weak feedback on the cold gas from both AGN and starburst activity; (2) The dynamically inferred SMBH mass is 1.6 +/- 0.4 (rnd) +/- 0.8 (sys) x 10^8 Msun, assuming that we have accurately subtracted the AGN and starburst light contributions, which have a luminosity of about 10^9 Lsun; (3) The SMBH mass agrees with the SMBH-stellar mass relation but is about 50 times higher than previous estimates from X-ray variability; (4) The dynamically inferred molecular gas mass is 30 times smaller than that inferred from adopting the Galactic CO-to-H_2 conversion factor (X_CO) for thermalised gas, suggesting low values of X_CO; (5) the molecular gas inflow rate increases steadily with radius and may be as high as 5 Msun/yr. This work highlights the potential of using high-resolution CO data to estimate, in addition to SMBH masses, the X_CO factor and gas inflow rates in nearby galaxies.