Reproducing Abell 2744 with the HyperMillennium simulation

ABSTRACT We present the HyperMillennium (HM) simulation, an extremely large cosmological simulation designed to support next-generation galaxy surveys. The simulation follows 4.2 trillion dark matter particles in a comoving box of $2.5\ {h^{-1}\rm Gpc}$, with a mass resolution of $3.2 \times 10^8\, {h^{-1}\rm {\rm M}_{\odot }}$ and a force resolution of $3.0\ {h^{-1}\rm kpc}$. Its combination of scale and resolution is ideal for studying large-scale structures and rare cosmic objects. In this first paper of the HM project, we explore whether the massive galaxy cluster Abell 2744 (A2744) can be reproduced in detail in the simulation. Pixel-based statistics of galaxy number density $N_{\rm gal}$, luminosity density $L_{\rm gal}$, and projected mass density $\kappa$ show excellent agreement between A2744 and its analogues down to $\sim 50$ kpc, once field-selection biases towards high galaxy surface density are accounted for. This concordance, achieved in one of the most extreme known galaxy environments, is a validation of the underlying $\Lambda {\rm CDM}$ model in the extreme regime of A2744. It also showcases the robustness and accuracy of the HM simulation, which, when coupled with a sophisticated semi-analytic galaxy formation model, is capable of producing galaxy and mass catalogues of comparable quality out to high redshift across its full comoving volume of 50.4 ${\rm Gpc^3}$.