The imprints of bars on the vertical stellar population gradients of
  galactic bulges
  This is the second paper of a series aimed to study the stellar kinematics
and population properties of bulges in highly-inclined barred galaxies. In this
work, we carry out a detailed analysis of the stellar age, metallicity and
[Mg/Fe] of 28 highly-inclined ($i > 65^{o}$) disc galaxies, from S0 to S(B)c,
observed with the SAURON integral-field spectrograph. The sample is divided
into two clean samples of barred and unbarred galaxies, on the basis of the
correlation between the stellar velocity and h$_3$ profiles, as well as the
level of cylindrical rotation within the bulge region. We find that while the
mean stellar age, metallicity and [Mg/Fe] in the bulges of barred and unbarred
galaxies are not statistically distinct, the [Mg/Fe] gradients along the minor
axis (away from the disc) of barred galaxies are significantly different than
those without bars. For barred galaxies, stars that are vertically further away
from the midplane are in general more [Mg/Fe]--enhanced and thus the vertical
gradients in [Mg/Fe] for barred galaxies are mostly positive, while for
unbarred bulges the [Mg/Fe] profiles are typically negative or flat. This
result, together with the old populations observed in the barred sample,
indicates that bars are long-lasting structures, and therefore are not easily
destroyed. The marked [Mg/Fe] differences with the bulges of unbarred galaxies
indicate that different formation/evolution scenarios are required to explain
their build-up, and emphasizes the role of bars in redistributing stellar
material in the bulge dominated regions.
