Estimating the Ages of Bars: Implications for the Bar-AGN-Star Formation   Connection
  In an effort to elevate to higher grounds our understanding on the impact of the formation and evolution of bars in the formation and evolution of galaxies, we have developed a diagnostic tool to distinguish between recently formed and evolved bars. Our method was applied in the study of a sample of 14 galaxies and revealed that, apparently, AGN activity tends to appear in galaxies which have young bars rather than evolved bars. This suggests that the time scale for the fueling of AGN by bars is short, and may help to explain, for instance, why there is not a clear correlation between the presence of bars and AGN in galaxies. 
Dimitri A. Gadotti, Ronaldo E. de Souza (Astronomy Department -   University of Sao Paulo)