Dr. KANAK SAHA

Recent cosmological hydrodynamical simulations suggest that a galactic disk could have assembled either around a merger-built classical bulge or as a pure disk galaxy. Soon after their formation, such disks go through rapid dynamical evolution, where minor mergers, star burst triggered by inflowing gas, and turbulence play dominant roles. However, as these violent episodes become less frequent, secular processes start dominating the subsequent evolution of disk galaxies. In this talk, the speaker will show how secular evolution brings morphological and dynamical changes to the disk leading to the eventual formation of pseudo-bulges. Not only disk, but a preexisting classical bulge undergoes substantial dynamical changes. This happens through the formation of non-axisymmetric structures such as bars, spiral arms, lopsidedness and warps, which facilitate the exchange and eventual redistribution of energy and angular momentum between the disk, bulge and the dark matter halo. The speaker will show how the dark matter halos participate in the secular evolution. Finally, he will briefly discuss how to construct a theoretical framework to describe secular evolution.