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 .