Navarro–Frenk–White profile

The Navarro–Frenk–White (NFW) profile is one of the most commonly used models for the structure of dark matter halos.. It describes the average density of dark matter in galaxy and galaxy cluster halos as a function of distance from their center. It was originally proposed on the basis of N-body simulations by Julio Navarro, Carlos Frenk and Simon White. The substantial impact of this work on the theoretical understanding of cosmic structure formation can be traced to three key insights.

1) In cosmological models where dark matter structure grows hierarchically from weak initial fluctuations, dark matter halos are almost self-similar; halo regions which are close to dynamical equilibrium are adequately represented for all masses and at all times by a simple analytic formula with only two free parameters, a characteristic density and a characteristic size.

2) These two parameters are related with rather little scatter; larger halos are less dense. The size-density relation depends on cosmological parameters and so can be used to constrain these observationally.

3) The characteristic density of a halo is linked to the mean density of the universe at its epoch of maximal growth. Thus the size-density relation reflects the fact that larger halos typically assembled at later times.