Speaker
Description
Despite most supermassive black hole (SMBH) growth occurring via merger-free processes, the underlying mechanisms driving this secular evolution are poorly understood. We investigate the role that both strong and weak large-scale galactic bars play in mediating this growth, by analysing the active galactic nucleus (AGN) fraction in strongly barred, weakly barred, and unbarred galaxies up to z = 0.1, with a median z=0.067. We find an optically selected AGN fraction of 31.6 ± 0.9 % in strongly barred galaxies, 23.3 ± 0.8 % in weakly barred galaxies, and 14.2 ± 0.6 % in unbarred disc galaxies. These are highly statistically robust results, strengthening the tantalising findings 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. Thus, while bars are not required in order to grow an SMBH in a disc galaxy, 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 than an unbarred galaxy at all galaxy stellar masses and colours. With this robust correlation now demonstrated, we can look at the complex interplay between AGN, bars, and galactic bulges. Since bulges can be grown via the inflow of gas driven by bars, and a number of scaling relationships demonstrate a correlation between AGN and bulges, disentangling these processes will illuminate secular fuelling, furthering our understanding of galaxy evolution as a whole.
