WISDOM project -- XI. Star Formation Efficiency in the Bulge of the AGN-host Galaxy NGC 3169 with SITELLE and ALMA

TL;DR

This study investigates the spatial variation of star formation efficiency in the bulge of galaxy NGC 3169 using combined optical and radio observations, revealing a star-forming ring and central suppression linked to AGN feedback.

Contribution

It provides the first spatially-resolved analysis of SFE in the bulge of an AGN-host galaxy using SITELLE and ALMA data, highlighting the impact of AGN feedback and bulge dynamics.

Findings

Star-forming ring at ~1.25 kpc with low depletion time (~0.3 Gyr)

Increased gas depletion times (< 2.3 Gyr) towards the galaxy center

AGN feedback and bulge dynamics influence SFE radial profile

Abstract

The star formation efficiency (SFE) has been shown to vary across different environments, particularly within galactic starbursts and deep within the bulges of galaxies. Various quenching mechanisms may be responsible, ranging from galactic dynamics to feedback from active galactic nuclei (AGN). Here, we use spatially-resolved observations of warm ionised gas emission lines from the imaging Fourier transform spectrograph SITELLE at the Canada-France-Hawaii Telescope (CFHT) and cold molecular gas (CO(2-1)) from the Atacama Large Millimeter/sub-millimeter Array (ALMA) to study the SFE in the bulge of the AGN-host galaxy NGC 3169. After distinguishing star-forming regions from AGN-ionised regions using emission-line ratio diagnostics, we measure spatially-resolved molecular gas depletion times (\tau_dep = 1/SFE) with a spatial resolution of \approx 100 pc within a galactocentric radius of 1.8 kpc. We identify a star-forming ring located at radii 1.25 \pm 0.6 kpc with an average \tau_dep of 0.3 Gyr. At radii < 0.9 kpc, however, the molecular gas surface densities and depletion times increase with decreasing radius, the latter reaching approximately 2.3 Gyr at a radius \approx 500 pc. Based on analyses of the gas kinematics and comparisons with simulations, we identify AGN feedback, bulge morphology and dynamics as the possible causes of the radial profile of SFE observed in the central region of NGC 3169.