Pairwise Velocities of Dark Matter Halos: a Test for the Lambda Cold Dark Matter Model using the Bullet Cluster

Understand

The existence of 1E0657-56 poses a challenge to the concordance Lambda cold dark matter model.

• Here we investigate the velocity distribution of dark matter halo pairs in large N-body simulations with differing box sizes (250Mpc/h-2 Gpc/h) and resolutions.
• We examine statistics such as the halo masses, pairwise halo velocities (v_{12}), and pair separation distances.
• We then compare our results to the initial conditions (ICs) required to reproduce the observational properties of 1E0657-56 in non-cosmological hydrodynamical simulations.