Galaxies with nested bars: constraining their formation scenarios

Secular evolution theory predicts that spheroidal components are formed thanks to bars that can transport gas to the central regions of the galaxies. This activity would trigger the star formation needed to generate galactic bulges. According to this idea, bars at smaller scales may carry material to the galactic center and feed active galactic nuclei. For the first time, we have carried out a complete kinematical and stellar population analysis of a double-barred galaxy (NGC 357) to determine if this system of two bars is efficient enough to cause that kind of effects. We have measured suitable line-strength indices on high quality spectra to obtain the relative ages and metallicities for the different structural components and thus constrain the star formation history. First results seems to indicate that in the case of NGC 357 the nuclear bar hasn't played an important role in fueling the star formation in the center.