The Aquarius Project: Cold Dark Matter under a Numerical Microscope

Abstract

The ‘Aquarius’ project currently performs the first ever one-billion particle simulation of a Milky Way-sized dark matter
halo, improving resolution by a factor of more than 15 relative to previously published simulations of this type. This enables
dramatic advances in our understanding of the structure and substructure of dark matter in our Galaxy. Our project seeks clues
to the nature of the dark matter and aims to advance strategies for exploring the formation of our Galaxy, for searching for
signals from dark matter annihilation, and for designing experiments for direct detection of dark matter. Here we report on
the status of our calculations carried out on the HLRB-2 thus far, and discuss some of the early results we obtained. Our
results show much better convergence for the properties of dark matter substructures than ever reported in the literature
before. For the first time, we can reliably probe the central dark matter density cusp into a regime where the local logarithmic
slope becomes shallower than−1. We also provide a description of the simulation code GADGET-3 developed specifically for
this project, and highlight the new parallelization techniques we employed to deal with the extremely tightly coupled nature
and high dynamic range of our simulations.