Galaxy Formation from a Low-Spin Density Perturbation in a CDM Universe

Abstract

In order to understand the formation process of elliptical galaxies which are not rotationally supported, we have carried out numerical simulations of the galaxy formation from the density perturbation with a rotation corresponding to a small spin parameter. The three-dimensional TREE N-Body/SPH simulation code used in this paper includes the dark matter and gas dynamics, radiative cooling, star formation, supernova feedback, and metal enrichment. The initial condition is a slowly rotating, top-hat over-dense sphere on which the perturbations expected in a cold dark matter (CDM) universe are superposed. By means of the stellar population synthesis, we calculated the surface brightness profile, the metallicity distribution, and the photometric properties of the end-product, and found that these properties quantitatively agree with the observed properties of bright elliptical galaxies. Thus, we conclude that, in a CDM universe, the proto-galaxy which has a spin-parameter as small as 0.02 evolves into an elliptical galaxy.