BAR STRENGTH AND STAR-FORMATION ACTIVITY IN LATE-TYPE BARRED GALAXIES

With the prime aim of better probing and understanding the intimate li nk between star formation activity and the presence of bars, a represe ntative sample of 32 non-interacting late-type galaxies with well-dete rmined bar properties has been selected. We show that all the galaxies displaying the highest current star forming activity have both strong and long bars. Conversely not all strong and long bars are intensivel y creating stars. Except for two cases, strong bars are in fact long a s well. Numerical simulations allow to understand these observational facts as well as the connection between bar axis ratio, star formation activity, and chemical abundance gradient: Very young strong bars are first characterized by a raging episode of star formation and two dif ferent radial gaseous abundance gradients, one steep in the bar and on e shallow in the disc. Then, principally due to gas consumption, galax ies progressively fall back in a more quiescent state with a nearly fl at abundance gradient across the whole galaxy. On the contrary, weak b ars are unable to trigger significant star formation or to generate fl at abundance gradients. The selected galaxies have tentatively been cl assified in four classes corresponding to main stages of secular evolu tion scenario.