Scaling Evolution of Universal Dark Matter Halo Density Profiles

Dark-matter halos show a universal density profile with a scaling such thatless massive systems are typically denser. This mass-density relation is welldescribed by a proportionality between the characteristic density of halos andthe mean cosmic density at halo formation time. It has recently been shown thatthis proportionality could be the result of the following simple evolutionarypicture. Halos form in major mergers with essentially the same,cosmogony-dependent, dimensionless profile, and then grow inside-outside, as aconsequence of accretion. Here we verify the consistency of this picture andshow that it predicts the correct zero point of the mass-density relation.Comment: 9 pages, 1 Table and 1 postscript figure, latex uses aaspp4.sty, accepted for publication in The Astrophysical Journal Letter