Resolving infall caustics in dark matter halos

TL;DR

This paper reveals that dark matter halos contain well-defined phase-space structures with velocity streams, which create observable peaks in velocity distributions, aligning with predictions from the secondary infall model.

Contribution

It demonstrates the existence of fine-grained phase-space structures in simulated dark matter halos and links these features to the secondary infall model.

Findings

Distinct velocity streams with high density contrast in halos

Peaks in velocity distribution due to accreted particles

Overall structure consistent with secondary infall model

Abstract

We have found that the phase-space of a dark matter particles assembling a galactic halo in cosmological N-body simulations has well defined fine grained structure. Recently accreted particles form distinctive velocity streams with high density contrast. For fixed observer position these streams lead to peaks in velocity distribution. Overall structure is close to that emerging in the secondary infall model.