The Origin of Dark Matter Halo Profiles
  A longstanding puzzle of fundamental importance in modern cosmology has been
the origin of the nearly universal density profiles of dark matter halos found
in N-body simulations -- the so-called NFW profile. We show how this behavior
may be understood, simply, by applying adiabatic contraction to peaks of
Gaussian random fields. We argue that dynamical friction acts to reduce
enormously the effect of random scatter in the properties of initial peaks,
providing a key simplification. We compare our model predictions with results
of the ultra-high resolution Via Lactea-II N-body simulation, and find superb
agreement. We show how our model may be used to predict the distribution of
halo properties like concentration. Our results suggest that many of the basic
properties of halo structure may be understood using extremely simple physics.
