Distinct stellar populations in the inner bars of double-barred galaxies
  Numerical simulations of double-barred galaxies predict the build-up of
different structural components (e.g., bulges, inner discs) in the central
regions of disc galaxies. In those simulations, inner bars have a prominent
role in the internal secular evolution of their host galaxies. The development
of bulges and inner discs is, however, poorly understood observationally due to
the small number of studies focusing on the stellar populations of these
systems. In order to provide constraints on the relevant processes inducing the
creation of these components in the presence of inner bars, we have carried out
a detailed kinematical and stellar population analysis in a sample of four
double-barred galaxies, ranging from SB0 to SBb, observed with integral-field
spectroscopy. We find that the inner bars present distinct stellar population
properties, being younger and more metal-rich than the surrounding bulges and
outer bars. While we detect signatures of gas inflow through the inner bars, we
find no evidence of associated star-forming regions or newly-formed structures
around them. This result suggests that, regardless of their formation scenario,
at present these inner bars are playing a moderate or even a minor role in the
morphological evolution of this sample of double-barred galaxies.
