HADES: a new numerical tool for the determination of DM over-densities

Cosmological simulations predict dark matter to form bound structures (i.e. main halos), hosting galaxies and eventually a population of less massive dark matter over-densities, (i.e. sub-halos). The determination of the spatial dark matter distribution in halos and sub-halos is one major challenge in the analysis of galaxy formation simulations, and usually relies on halo finder algorithms coupled with approximated analytical density profiles. Such determination is crucial for deriving, among others, dark matter signatures in astroparticle observables, e.g. the flux of gamma-ray photons from dark matter particle annihilation. We present here the "Halo Accurate Density Evaluation System" (HADES) a novel numerical tool to reconstruct the dark matter density locally at any point in the simulation volume with high accuracy. We run thorough tests of the code performances on dedicated mock realisations of halos starting from analytical dark matter profile distributions. We show that on mock halos HADES can recover the dark matter density with a few $\%$ accuracy, resolving efficiently all sub-structures containing down to 1000 particles and providing conservative estimates for smaller sub-halos. We illustrate how HADES can be used to compute all-sky maps of the dark matter spatial distribution, squared and integrated along the line of sight, already accounting for the signal boosting coming from density fluctuations. We also present an application of the code to one halo in the TNG50-1-Dark simulation from the IllustrisTNG suite, and highlight how HADES automatically maps out the asymmetries present in the dark matter spatial distribution both in halos and sub-halos, promising to become a helpful tool for a vast number of astrophysical applications.