Abell 2744: Too much substructure for Lambda CDM?

Abstract

The massive substructures found in Abell 2744 by Jauzac et al. (2016) present a challenge to the cold dark matter paradigm due to their number and proximity to the cluster centre. We use one of the biggest N-body simulations, the Millennium XXL, to investigate the substructure in a large sample of massive dark matter haloes. A range of effects which influence the comparison with the observations is considered, extending the preliminary evaluation carried out by Jauzac et al. (2016). There are many tens of haloes in the simulation with a total mass comparable with or larger than that of Abell 2744. However, we find no haloes with a number and distribution of massive substructures (> 5 10^13 Msun) that is close to that inferred from the observations of Abell 2744. The application of extreme value statistics suggests that we would need a simulation of at least ten times the volume of the Millennium XXL to find a single dark matter halo with a similar internal structure to Abell 2744. Explaining the distribution of massive substructures in clusters is a new hurdle for hierarchical models to negotiate, which is not weakened by appeals to baryonic physics or uncertainty over the nature of the dark matter particle.

12 pages, 5 figures, Accepted for publication in MNRAS, V2: minor changes in the manuscript

References in corpus (8)

• Introducing the Illustris Project: Simulating the coevolution of dark and visible matter in the Universe
• Concentration, Spin and Shape of Dark Matter Haloes as a Function of the Cosmological Model: WMAP1, WMAP3 and WMAP5 results
• CLASH-VLT: Insights on the mass substructures in the Frontier Fields Cluster MACS J0416.1-2403 through accurate strong lens modeling
• Using the Milky Way satellites to study interactions between cold dark matter and radiation
• The Structure of Halos: Implications for Group and Cluster Cosmology
• Substructure in lensing clusters and simulations
• Implications of multiple high-redshift galaxy clusters
• Local Group galaxies emerge from the dark

Cited by in corpus (2)

• HBT+: an improved code for finding subhalos and building merger trees in cosmological simulations
• Abell 2744 may be a supercluster aligned along the sightline