Halo growth and the NFW profile

We perform a simple test showing that accreting halos grow inside-out and have density profiles that are statistically indistinguishable from those of halos having undergone major mergers. The test also reveals that the ability for the NFW analytical expression to fit the density profile of halos spoils towards large masses at any redshift. On view of these results, we analyze the M-c relations on extreme mass and redshift domains predicted by usual toy models based on numerical data and one physical model based on the two assumptions above confirmed by the test.