Formation of elliptical galaxies and massive halos
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Abstract
In the present N-body models for the formation of spheroids of galaxies, the material starts in uniform expansion. For the dissipationless case, turnaround and collapse accompanied by the formation and destruction of substructure yields a smooth object, similar to an elliptical galaxy, whose core density is low and outer density gradient too steep. Dissipation is added with a simple scheme of 'sticky' particle collisions between neighboring gas clouds that turns them into collisionless 'stars' after a given specific number of collisions, yielding final densities that are closer to the r to the 1/4-power function. These experiments are extended to include a dissipationless and massive dark halo whose mass is 10 times greater than that of the gas. In the most extreme case of dissipation, the dark halo stars have isotropic velocity dispersions.