Galaxy Zoo: the effect of bar-driven fueling on the presence of an
  active galactic nucleus in disc galaxies
  We study the influence of the presence of a strong bar in disc galaxies which
host an active galactic nucleus (AGN). Using data from the Sloan Digital Sky
Survey and morphological classifications from the Galaxy Zoo 2 project, we
create a volume-limited sample of 19,756 disc galaxies at $0.01<z<0.05$ which
have been visually examined for the presence of a bar. Within this sample, AGN
host galaxies have a higher overall percentage of bars (51.8%) than inactive
galaxies exhibiting central star formation (37.1%). This difference is
primarily due to known effects; that the presence of both AGN and galactic bars
is strongly correlated with both the stellar mass and integrated colour of the
host galaxy. We control for this effect by examining the difference in AGN
fraction between barred and unbarred galaxies in fixed bins of mass and colour.
Once this effect is accounted for, there remains a small but statistically
significant increase that represents 16% of the average barred AGN fraction.
Using the $L_{\rm{[O III]}}/M_{BH} $ratio as a measure of AGN strength, we show
that barred AGN do not exhibit stronger accretion than unbarred AGN at a fixed
mass and colour. The data are consistent with a model in which bar-driven
fueling does contribute to the probability of an actively growing black hole,
but in which other dynamical mechanisms must contribute to the direct AGN
fueling via smaller, non-axisymmetric perturbations.
