Dissipationless collapses in modified Newtonian dynamics

Dissipationless collapses in modified Newtonian dynamics (MOND) are studied by using a new particle-mesh N-body code based on our numerical MOND potential solver. We found that low surface density end products have shallower inner density profiles, flatter radial velocity dispersion profiles, and more radially anisotropic orbital distributions than high surface density end products. The projected density profiles of the final virialized systems are well described by Sersic profiles with index m less than or similar to 4, down to m similar to 2 for a deep MOND collapse. Consistent with observations of elliptical galaxies, the MOND end products, if interpreted in the context of Newtonian gravity, would appear to have little or no dark matter within the effective radius. However, we found it impossible ( under the assumption of constant stellar mass-to-light ratio) to simultaneously place the resulting systems on the observed Kormendy, Faber-Jackson, and fundamental plane relations of elliptical galaxies. Finally, the simulations provide strong evidence that phase mixing is less effective in MOND than in Newtonian gravity.