Shock and splash: gas and dark matter halo boundaries around ΛCDM galaxy clusters

ABSTRACT Recent advances in simulations and observations of galaxy clusters suggest that there exists a physical outer boundary massive cluster-size dark matter (DM) haloes. In this work, we investigate the locations boundaries DM gas around haloes, by analysing sample 65 haloes extracted from Omega500 zoom-in hydrodynamical cosmological simulations. We show location accretion shock is offset splashback radius, contrary to prediction self-similar models. The radius larger than all definitions literature $20-100{{\ \rm per\ cent}}$. defined using steepest drop entropy pressure profiles approximately 1.89 times slope density profile, it ≈1.2 edge phase space structure. discuss implications our results for multiwavelength studies clusters.