Simulations of the Formation and Evolution of Galactic Disks in the Expanding Universe

Daniel Ceverino-Rodriguez

Galaxy formation and evolution is a challenging problem because some key physical processes are still not well understood and their effects on galactic scales are not clear. These effects include the formation of stars inside gaseous clouds and feedback processes such as supernova explosions. We are going to address the issue of formation of galactic disks using a N-body + gasdynamic code in which these key processes are included: radiative cooling and heating of a plasma with a given metallicity, star formation and stellar feedback which includes thermal feedback and metal enrichment. We are trying to find a more realistic treatment of these processes.

Due to the difficulties of full hydrodynamical simulations, we have also studied the evolution of galactic disks from a different perspective. Once the stellar disk is formed, we consider that a big fraction of the gas in the disk is converted into stars. Then, we can assume that the remaining gas does not affect the evolution of the stellar distribution. In this approximation, we neglect all hydrodynamical processes and treat the disk as a N-body system. Then, we can use only N-body simulations to study the long-term evolution of an already formed stellar disk. We have focused on the evolution of galactic disks which develop strong bars in their centers. We found dynamical resonances between the bar and disk or halo material. These resonances can capture stars near certain resonant orbits. As a result, resonances prevent the evolution of the stars trapped around these orbits.