Resolution of the apparent discrepancy between the number of massive subhaloes in Abell 2744 and ΛCDM

Abstract

Schwinn et al. (2017) have recently compared the abundance and distribution of massive substructures identified in a gravitational lensing analysis of Abell 2744 by Jauzac et al. (2016) and N-body simulation and found no cluster in ΛCDM simulation that is similar to Abell 2744. Schwinn et al.(2017) identified the measured projected aperture masses with the actual masses associated with subhaloes in the MXXL N-body simulation. We have used the high resolution Phoenix cluster simulations to show that such an identification is incorrect: the aperture mass is dominated by mass in the body of the cluster that happens to be projected along the line-of-sight to the subhalo. This enhancement varies from factors of a few to factors of more than 100, particularly for subhaloes projected near the centre of the cluster. We calculate aperture masses for subhaloes in our simulation and compare them to the measurements for Abell 2744. We find that the data for Abell 2744 are in excellent agreement with the matched predictions from ΛCDM. We provide further predictions for aperture mass functions of subhaloes in idealized surveys with varying mass detection thresholds.

5 pages, 5 figures. Accepted for publication in MNRAS Letter

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• Uncovering substructure with wavelets: proof of concept using Abell 2744
• Intra-Cluster Light as a Dynamical Clock for Galaxy Clusters: Insights from the MAGNETICUM, IllustrisTNG, Hydrangea and Horizon-AGN Simulations
• Mapping dark matter and finding filaments: calibration of lensing analysis techniques on simulated data
• A Redshift Survey of the Coma Cluster (A1656): Understanding the Nature of Subhalos in the Weak-lensing Map
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