Dynamical Evolution of Disk Galaxies

    No single theory is perfect for explaining the galaxy formation and evolution framework across all galactic morphologies as framed by the Hubble galaxy morphological classification diagram (Hubble 1926). To date, the astrophysical community has a fair understanding of the formation mechanism of early-type galaxies like ellipticals via monolithic collapse model, major merger model, multiphase dissipational collapse model, accretion and in-situ hierarchical merger model, etc. However, such theories failed to explain the formation and evolution of late-type galaxies like spirals and lenticulars. More comprehensive frameworks are required to describe them. The complexity of these systems, involving structures like stellar bars, spiral arms, rings, boxy/peanut bulges, etc., necessitates advanced computational approaches for analysis and simulation.

The study of disk galaxies (spirals and lenticulars) is pivotal for understanding the formation of large-scale structures in the universe. Unlike old galaxies like ellipticals, where star formation has largely ceased, disk galaxies are relatively younger and have a constant star formation rate. Thus, studying their dynamics is crucial to understanding how structures like bars, spiral arms, rings, boxy/peanut bulges, etc. are formed therein. Disk galaxies can exhibit both ordered and chaotic motions in various ways. The ordered motion is characterized by rotating stars and gas in a well-defined direction around the galactic centre. In contrast, chaotic motions are generated from instabilities produced in the central region due to the propagation of density waves.