Nonlinear evolution of dark matter subhalos and applications to warm dark matter

TL;DR

This paper develops a semi-analytic method to model nonlinear evolution of dark matter subhalos, including tidal effects, and compares subhalo properties in cold and warm dark matter scenarios to aid in distinguishing between them.

Contribution

It introduces a new semi-analytic framework incorporating tidal effects for subhalo evolution, calibrated to simulations, and applies it to compare CDM and WDM models.

Findings

Tidal effects dominate nonlinear subhalo evolution.

Subhalo mass functions differ between CDM and WDM.

Probes of substructure can distinguish dark matter types.

Abstract

We describe the methodology to include nonlinear evolution, including tidal effects, in the computation of subhalo distribution properties in both cold (CDM) and warm (WDM) dark matter universes. Using semi-analytic modeling, we include effects from dynamical friction, tidal stripping, and tidal heating, allowing us to dynamically evolve the subhalo distribution. We calibrate our nonlinear evolution scheme to the CDM subhalo mass function in the Aquarius N-body simulation, producing a subhalo mass function within the range of simulations. We find tidal effects to be the dominant mechanism of nonlinear evolution in the subhalo population. Finally, we compute the subhalo mass function for $m_\chi=1.5$ keV WDM including the effects of nonlinear evolution, and compare radial number densities and mass density profiles of subhalos in CDM and WDM models. We show that all three signatures differ between the two dark matter models, suggesting that probes of substructure may be able to differentiate between them.