Formation and evolution of galaxy disks: what is wrong with CDM?

Abstract

We find that the density distribution of high and low surface brightness (SB) galaxy disks formed within LCDM halos under the assumption of detailed angular momentum conservation is in rough agreement with observations. The luminous-to-dark matter ratio of the model galaxies increases with SB. The lowest SB models tend to be minimum disks, but the high SB models hardly attain the maximum disk solution. With the introduction of shallow cores in the halos, high SB models become maximum disks. The shallow cores also help to improve the inner SB profiles of bulge-less low SB models and the zero-point of the Tully-Fisher relation. The models predict well this relation and its scatter, as well as the small correlation among the residuals of this and the luminosity-radius relation, in spite of the dependence of the rotation curve shapes on SB.