DISSIPATIVE PROCESS AS A MECHANISM OF DIFFERENTIATING INTERNAL STRUCTURES BETWEEN DWARF AND NORMAL ELLIPTICAL GALAXIES IN A COLD DARK MATTER UNIVERSE

摘要

We simulate thc dynamical, chemical, and spectrophotometric evolution of dwarf and normal elliptical galaxies embedded in a dark matter halo using a three-dimensional N-body/smoothed particle hydrodynamics simulation code. For the forming dwarf clliptical galaxies, supernova-driven winds propagating outward from inside the system collide with the infalling gas and produce the supershell in which stars are formed. The resulting stellar system forms a loosely bound virialized system due to the significant mass loss and has a large velocity dispersion and a large core. Consequent1y the surface brightness distribution shows an exponential profile and the color distribution shows a positive gradient such that the colors become redder away from the galaxy center in agreement with observations. On the other hand, for the normal elliptical galaxies with deep gravitational potential, the mass loss out of the system does not have a significant dynamical effect on the stellar system. The resulting surface brightness distribution has a large central concentration like de Vaucouleurs' r~1/4 profile and the color distribution shows a negative gradient as observed. Our simulation shows that different features between dwarf and normal elliptical galaxies stem from different cooling efficiencies for their respective protogalaxies in a standard cold dark matter universe.