Aspects of Bar Evolution: BP Bulges, Shoulders and Clumps
Victor Debattista - UCLan
Aula Seminari DAM (7th floor)
Asbtract: I review some recent results on the evolution of bars. Box/Peanut (BP) bulges are well-known to be caused by the vertical thickening of bars. The fraction of bars that hosts such BP bulges is a strong function of mass, but to date the cause of this behaviour has not been understood. I present evidence that the BP fraction is a result of galaxy downsizing, with bars in lower mass galaxies being younger. This means the bars have not had enough time to form a BP bulge. Another property of bars which has long been known is that they often have an excess density above an exponential, which we refer to as `shoulders'. New observational results suggest that shoulders and BP bulges are related, with the formation of shoulders preceding that of BPs. Simulation studies show that the shoulders are a symptom of a growing bar, and orbital studies show that the orbits supporting shoulders need to be constantly replenished. Lastly I present evidence that high star formation rate clumps have played a role in the formation of the Milky Way’s bulge.