Dissipative Process as a Mechanism of Differentiating Internal Structures between Dwarf and Normal Elliptical Galaxies in a Cold Dark Matter Universe

We simulate the dynamical, chemical, and spectro-photometric evolution ofdwarf and normal elliptical galaxies embedded in a dark matter halo, using athree-dimensional N-body/SPH simulation code. For the forming dwarf ellipticalgalaxies, supernova-driven winds propagating outwards from inside the systemcollide with the infalling gas and produce the super-shell in which stars areformed. The resulting stellar system forms a loosely bound virialized systemdue to the significant mass loss and has a large velocity dispersion and alarge core. Consequently the surface brightness distribution shows anexponential profile and the color distribution shows a positive gradient suchthat the colors become redder away from the galaxy center in agreement withobservations. On the other hand, for the normal elliptical galaxies with deepgravitational potential, the mass loss out of the system does not have asignificant dynamical effect on the stellar system. The resulting surfacebrightness distribution has a large central concentration like de Vaucouleurs'$r^{1/4}$-profile and the color distribution shows a negative gradient asobserved. Our simulation shows that different features between dwarf and normalelliptical galaxies stem from different cooling efficiencies for theirrespective protogalaxies in a standard CDM universe.Comment: 15 pages, 12 figures, to appear in the ApJ, issue of February 1, 199