Suppression of Star Formation in NGC 1266

TL;DR

This study shows that low-power AGN-driven outflows in NGC 1266 significantly suppress star formation by hindering gas fragmentation, indicating common AGNs can influence galaxy evolution.

Contribution

It provides detailed millimeter observations demonstrating that even low-power AGNs can suppress star formation through turbulent outflows, a novel insight into galaxy feedback mechanisms.

Findings

Most molecular gas cannot escape the galaxy.

Star formation is suppressed by a factor of 50-150.

AGN-driven turbulence hinders star formation processes.

Abstract

NGC1266 is a nearby lenticular galaxy that harbors a massive outflow of molecular gas powered by the mechanical energy of an active galactic nucleus (AGN). It has been speculated that such outflows hinder star formation (SF) in their host galaxies, providing a form of feedback to the process of galaxy formation. Previous studies, however, indicated that only jets from extremely rare, high power quasars or radio galaxies could impart significant feedback on their hosts. Here we present detailed observations of the gas and dust continuum of NGC1266 at millimeter wavelengths. Our observations show that molecular gas is being driven out of the nuclear region at $\dot{M}_{\rm out} \approx 110 M_\odot$ yr$^{-1}$, of which the vast majority cannot escape the nucleus. Only 2 $M_\odot$ yr$^{-1}$ is actually capable of escaping the galaxy. Most of the molecular gas that remains is very inefficient at forming stars. The far-infrared emission is dominated by an ultra-compact ($\lesssim50$pc) source that could either be powered by an AGN or by an ultra-compact starburst. The ratio of the SF surface density ($\Sigma_{\rm SFR}$) to the gas surface density ($\Sigma_{\rm H_2}$) indicates that SF is suppressed by a factor of $\approx 50$ compared to normal star-forming galaxies if all gas is forming stars, and $\approx$150 for the outskirt (98%) dense molecular gas if the central region is is powered by an ultra-compact starburst. The AGN-driven bulk outflow could account for this extreme suppression by hindering the fragmentation and gravitational collapse necessary to form stars through a process of turbulent injection. This result suggests that even relatively common, low-power AGNs are able to alter the evolution of their host galaxies as their black holes grow onto the M-$\sigma$ relation.