The Hateful Eight: Matching the Massive Substructures of A2744 with Magneticum

Lucas C. Kimmig, Rhea-Silvia Remus, Veronica Biffi, and Klaus Dolag

Abstract

Gravitational (strong and weak) lensing observations report galaxy clusters with large numbers of very massive substructures seemingly in tension with ΛCDM simulations, such as Abell 2744. Utilizing the full power of the state of the art hydrodynamical cosmological simulation suite Magneticum pathfinder, I test whether this tension is a true tension or founded in differences of the methodology.

I will show, using a novel approach to facilitate more direct comparability to the observation methods, that the simulations can reproduce the observations when accounting for the impact of different orientations of the projected cluster mass distribution. Furthermore, I demonstrate that such richness in number and mass of substructure is evidence for a cluster in an assembling phase.

Finally, I find indications that the environment of the cluster when projected could additionally alter the results, where previous comparisons on the basis of Subfind fail to account for these effects.