The Dynamics of Subhalos in Warm Dark Matter Models

TL;DR

This study compares subhalo properties in Cold and Warm Dark Matter models, finding similar spatial distributions but differences in mass loss and velocities, suggesting observational tests may not distinguish these models effectively.

Contribution

It provides a detailed comparison of subhalo characteristics in WDM and CDM cosmologies, highlighting similarities and differences in their distributions and dynamics.

Findings

WDM subhalo density is suppressed compared to CDM.

Backsplash subhalos are present in both models.

WDM subhalos experience more mass loss.

Abstract

We present a comparison of the properties of substructure halos (subhalos) orbiting within host halos that form in Cold Dark Matter (CDM) and Warm Dark Matter (WDM) cosmologies. Our study focuses on selected properties of these subhalos, namely their anisotropic spatial distribution within the hosts; the existence of a "backsplash'' population; the age-distance relation; the degree to which they suffer mass loss; and the distribution of relative (infall) velocities with respect to the hosts. We find that the number density of subhalos in our WDM model is suppressed relative to that in the CDM model, as we would expect. Interestingly, our analysis reveals that backsplash subhalos exist in both the WDM and CDM models. Indeed, there are no statistically significant differences between the spatial distributions of subhalos in the CDM and WDM models. There is evidence that subhalos in the WDM model suffer enhanced mass loss relative to their counterparts in the CDM model, reflecting their lower central densities. We note also a tendency for the (infall) velocities of subhalos in the WDM model to be higher than in the CDM model. Nevertheless, we conclude that observational tests based on either the spatial distribution or the kinematics of the subhalo population are unlikely to help us to differentiate between the CDM model and our adopted WDM model.