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arXiv · 1505.05470

The offsets between galaxies and their dark matter in Lambda-CDM

Matthieu Schaller·Andrew Robertson·Richard Massey·Richard G. Bower·Vincent R. Eke
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Abstract

We use the "Evolution and Assembly of GaLaxies and their Environments" ( EAGLE ) suite of hydrodynamical cosmological simulations to measure offsets between the centres of stellar and dark matter components of galaxies. We find that the vast majority (>95%) of the simulated galaxies display an offset smaller than the gravitational softening length of the simulations (Plummer-equivalent $\epsilon = 700$ pc), both for field galaxies and satellites in clusters and groups. We also find no systematic trailing or leading of the dark matter along a galaxy's direction of motion. The offsets are consistent with being randomly drawn from a Maxwellian distribution with $\sigma \leq 196$ pc. Since astrophysical effects produce no feasible analogues for the $1.62^{+0.47}_{-0.49}$ kpc offset recently observed in Abell 3827, the observational result is in tension with the collisionless cold dark matter model assumed in our simulations.

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Matthieu Schaller, Andrew Robertson, Richard Massey, Richard G. Bower, Vincent R. Eke. 2015-05-20. The offsets between galaxies and their dark matter in Lambda-CDM. https://doi.org/10.1093/mnrasl%2Fslv104

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