Effect of bars in AGN host galaxies and black hole activity
  With the aim of assessing the effects of bars on active galactic nuclei
(AGN), we present an analysis of host characteristics and nuclear activity of
AGN galaxies with and without bars selected from the Sloan Digital Sky Survey
Data Release 7 (SDSS-DR7). By visual inspection of SDSS images we classified
the hosts of face-on AGN spiral galaxies brighter than g < 16.5 into barred or
unbarred. With the purpose of providing an appropriate quantification of the
effects of bars, we also constructed a suitable control sample of unbarred AGN
galaxies with similar redshift, magnitude, morphology, bulge sizes and local
environment distributions. We find that the bar fraction, with respect to the
full sample of spiral face-on AGN host galaxies, is 28.5%, in good agreement
with previous works. Barred AGN host galaxies show an excess of young stellar
populations dominated by red u-r and g-r colors, with respect to the control
sample, suggesting that bars produce an important effect on galaxy properties
of AGN hosts. Regarding the nuclear activity distribution, we find that barred
AGN galaxies show a shift toward higher Lum[OIII] values with respect to AGN
without bars. In addition, we also find that this trend is more significant in
less massive, younger stellar population and bluer AGN host galaxies. We found
that the fraction of powerful AGN increase towards more massive hosts with
bluer colors and younger stellar populations residing in denser environments.
However, barred host AGN systematically show a higher fraction of powerful
active nuclei galaxies with respect to the control sample. We also explored the
accretion rate onto the central black holes finding that barred AGN show an
excess of objects with high accretion rate values with respect to unbarred AGN
galaxies.
