Internal dark matter structure of the most massive galaxy clusters

We investigate the evolution of the dark matter density profiles of the most massive galaxy clusters in the Universe. Using a `zoom-in’ procedure on a large suite of cosmological simulations of total comoving volume of $3,(h^{-1},\rm Gpc)^3$,westudythe25mostmassiveclustersinfourredshiftslicesfrom$z\sim 1$tothepresent\mathrm{.}Theminimummassis$M_{500} > 5.5 \times 10^{14}$M${\odot}$at$z=1$\mathrm{.}Eachsystemhasmorethantwomillionparticleswithin$r{500}$. Once scaled to the critical density at each redshift, the dark matter profiles within $r_{500}$ are strikingly similar from $z\sim 1$ to the present day, exhibiting a low dispersion of 0.15 dex, and showing little evolution with redshift in the radial logarithmic slope and scatter. They have the running power law shape typical of the NFW-type profiles, and their inner structure, resolved to $3.8h^{-1}$ comoving kpc at $z=1$, shows no signs of converging to an asymptotic slope. Our results suggest that this type of profile is already in place at $z>1$ in the highest-mass haloes in the Universe, and that it remains exceptionally robust to merging activity.