Illuminating Dark Matter Halo Density Profiles Without Subhaloes

TL;DR

This paper investigates the density profiles of the smooth components of dark matter haloes by excluding subhaloes, revealing differences from traditional profiles and offering improved models for observational comparisons.

Contribution

It introduces a method to analyze smooth halo profiles excluding subhaloes, showing they differ from standard models and are better described by a generalized Einasto profile.

Findings

Smooth profiles decline more rapidly at large radii.

Concentrations from smooth profiles show less scatter and weaker mass dependence.

Generalized Einasto profile fits better than NFW or standard Einasto profiles.

Abstract

Cold dark matter haloes consist of a relatively smooth dark matter component as well as a system of bound subhaloes. It is the prevailing practice to include all halo mass, including mass in subhaloes, in studies of halo density profiles. However, often in observational studies satellites are treated as having their own distinct dark matter density profiles in addition to the profile of the host. This difference makes comparisons between theoretical and observed results difficult. In this work we investigate density profiles of the smooth components of host haloes by excluding mass contained within subhaloes. We find that the density profiles of the smooth halo component (without subhaloes) differs substantially from the conventional halo density profile. Smooth profiles decline more rapidly at large radii and are not well characterised by the standard NFW profile. We also find that concentrations derived from smooth density profiles exhibit less scatter at fixed mass and a weaker mass dependence than standard concentrations. Both smooth and standard halo profiles can be described by a generalised Einasto profile, an Einasto profile with a modified central slope, with smaller residuals than either an NFW or Einasto profile. These results hold for both Milky Way-mass and cluster-mass haloes. This new characterisation of smooth halo profiles can be useful for many analyses, such as lensing and dark matter annihilation, in which the smooth and clumpy components of a halo should be accounted for separately.