The BaLROG project - II. Quantifying the influence of bars on the
  stellar populations of nearby galaxies
  We continue the exploration of the BaLROG (Bars in Low Redshift Optical
Galaxies) sample: 16 large mosaics of barred galaxies observed with the
integral field unit SAURON. We quantify the influence of bars on the
composition of the stellar component. We derive linestrength indices of
H${\beta}$, Fe5015 and Mgb. Based on single stellar population (SSP) models, we
calculate ages, metallicities and [Mg/Fe] abundances and their gradients along
the bar major and minor axes. The high spatial resolution of our data allows us
to identify breaks among index and SSP profiles, commonly at 0.13$\pm$0.06 bar
length, consistent with kinematic features. Inner gradients are about ten times
steeper than outer gradients and become larger when there is a central rotating
component, implying that the gradients are not independent of dynamics and
orbits. Central ages appear to be younger for stronger bars. Yet, the bar
regions are usually old. We find a flattening of the iron (Fe5015) and
magnesium (Mgb) outer gradients along the bar major axis, translating into a
flattening of the metallicity gradient. This gradient is found to be
0.03$\pm$0.07 dex/kpc along the bar major axis while the mean value of the bar
minor axis compares well with that of an unbarred control sample and is
significantly steeper, namely -0.20$\pm$0.04 dex/kpc. These results confirm
recent simulations and discern the important localized influence of bars. The
elevated [Mg/Fe] abundances of bars and bulges compared to the lower values of
discs suggest an early formation, in particular for early type galaxies.
