The nature and nurture of bars and disks
  The effects that interactions produce on galaxy disks and how they modify the
subsequent formation of bars need to be distinguished to fully understand the
relationship between bars and environment. To this aim we derive the bar
fraction in three different environments ranging from the field to Virgo and
Coma clusters, covering an unprecedentedly large range of galaxy luminosities
(or, equivalently, stellar masses). We confirm that the fraction of barred
galaxies strongly depends on galaxy luminosity. We also show that the
difference between the bar fraction distributions as a function of galaxy
luminosity (and mass) in the field and Coma cluster are statistically
significant, with Virgo being an intermediate case. The fraction of barred
galaxies shows a maximum of about 50% at $M_r\,\simeq\,-20.5$ in clusters,
whereas the peak is shifted to $M_r\,\simeq\,-19$ in the field. We interpret
this result as a variation of the effect of environment on bar formation
depending on galaxy luminosity. We speculate that brighter disk galaxies are
stable enough against interactions to keep their cold structure, thus, the
interactions are able to trigger bar formation. For fainter galaxies the
interactions become strong enough to heat up the disks inhibiting bar formation
and even destroying the disks. Finally, we point out that the controversy
regarding whether the bar fraction depends on environment could be resolved by
taking into account the different luminosity ranges probed by the galaxy
samples studied so far.
