Galaxy Zoo: Bars in Disk Galaxies
  We present first results from Galaxy Zoo 2, the second phase of the highly
successful Galaxy Zoo project (www.galaxyzoo.org). Using a volume-limited
sample of 13665 disk galaxies (0.01< z < 0.06 and M_r<-19.38), we study the
fraction of galaxies with bars as a function of global galaxy properties like
colour, luminosity and bulge prominence. Overall, 29.4+/-0.5% of galaxies in
our sample have a bar, in excellent agreement with previous visually classified
samples of galaxies (although this overall fraction is lower than measured by
automated bar-finding methods). We see a clear increase in the bar fraction
with redder (g-r) colours, decreased luminosity and in galaxies with more
prominent bulges, to the extent that over half of the red, bulge-dominated,
disk galaxies in our sample possess a bar. We see evidence for a colour
bi-modality for our sample of disk galaxies, with a "red sequence" that is both
bulge and bar-dominated, and a "blue cloud" which has little, or no, evidence
for a (classical) bulge or bar. These results are consistent with similar
trends for barred galaxies seen recently both locally and at higher redshift,
and with early studies using the RC3. We discuss these results in the context
of internal (secular) galaxy evolution scenarios and the possible links to the
formation of bars and bulges in disk galaxies.
