Study of stellar populations in the bulges of barred galaxies
  We have obtained long-slit spectroscopy for a sample of 20 early-type barred
galaxies to study the influence of bars in the building of galaxy bulges. Line
strength indices were measured and used to derive age and metallicity gradients
in the bulge region by comparing with stellar population models. The same
analysis was also carried out with similar data of unbarred galaxies taken from
the literature. The bulges of barred galaxies seem to be more metal rich, at a
given velocity dispersion (sigma), than the bulges of unbarred galaxies, as
measured by some metallicity sensitive indices. There are indications that the
ratio of relative abundance of alpha-elements with respect to iron, [E/Fe],
derived for the bulges of barred galaxies tend to lie above the values of the
unbarred galaxies at a given sigma. The metallicity gradients for the majority
of the bulges are negative, less metal rich towards the end of the bulge. The
gradient values show a large scatter for galaxies with sigma below 150 km/s.
The age distribution is related to the presence of bulge substructure such as a
nuclear ring or an inner disk. The metallicity of both the bulge and the bar
are very well correlated indicating a close link between the enrichment
histories of both components. Bulges of barred early type galaxies might have
suffered a different chemical enrichment compared to the bulges of unbarred
galaxies of the same morphological type, same central velocity dispersion and
low inclination angles. The hinted stellar populations differences separating
the bulges of barred and unbarred galaxies and the strong link existing between
the metallicity of the bulge and the presence of a bar points to scenarios were
they both form simultaneously in processes leading to rapid and massive
episodes of star formation, possibly linked to the bar formation.
