Large-scale bars as a mechanism for triggering AGN

Despite the evidence that most supermassive black hole growth occurs via merger-free processes, the underlying mechanisms which drive their co-evolution with their host galaxies are poorly understood. I investigate the role that both strong and weak large-scale galactic bars play in mediating this relationship. I analyse the active galactic nucleus (AGN) fraction in strongly barred, weakly barred, and unbarred galaxies. After controlling for stellar mass and colour, I find that the AGN fraction is 31.6±0.9% in strongly barred galaxies, 23.3±0.8% in weakly barred, and 14.2±0.6% in unbarred. These are highly statistically robust results, strengthening the tantalising results in earlier works. Strongly barred galaxies have a higher fraction of AGN than weakly barred galaxies, which in turn have a higher fraction than unbarred galaxies. Large-scale galactic bars appear to facilitate AGN fuelling, and the presence of a strong bar makes a disc galaxy more than twice as likely to host an AGN.