5.5. Conclusion: Secular Evolution Processes in Barred Galaxies

I have reviewed recent progress toward an understanding of the many features seen in barred galaxies in terms of secular evolution processes driven by the bar. There are promising signs that even in complicated morphological descriptions such as (R)SB(rl)0 each symbol or feature has a well defined physical meaning. This is a first step toward a physical morphology of barred galaxies. The secular evolution processes identified to date are listed in Table 5. None of these processes is understood in detail. Furthermore, it is clear that such processes are concurrent and interdependent. For example, as long as a bar can grow by losing angular momentum to the disk, the signature of which is global spiral structure, it seems unlikely that it will evolve away by any interaction with the bulge. The study of secular evolution in barred galaxies is therefore a complicated problem which we have only begun to explore. However, the observations reviewed here support the idea that such evolution is taking place.