PROFESSOR KANAK SAHA

More than half of all galaxies in the local universe exhibit spiral structures in some form or the other and they form one of the basis for the Hubble tuning fork diagram. Origin and the nature of these many facet spiral structures continue to fascinate astronomers even today. In particular, whether spiral structures are long-lived have excited a fresh need to investigate this matter in detail. After a brief review, the speaker will discuss how long-lived grand design spiral structures are formed in collisionless simulations and the role of a central bulge in this regard. In addition to these, a few cases where wide open grand design spirals are formed and maintained for several billion years will be reported.