The Origin of Dark Matter Halo Profiles

TL;DR

This paper presents a simple physical model explaining the universal density profiles of dark matter halos, aligning well with high-resolution simulation results and predicting halo properties like concentration.

Contribution

It introduces a model based on adiabatic contraction and dynamical friction to explain halo profiles, simplifying the understanding of dark matter structure formation.

Findings

Model agrees with Via Lactea-II simulation results.

Predicts distribution of halo properties such as concentration.

Shows basic halo properties can be understood with simple physics.

Abstract

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.