Abstract
ABSTRACT The outskirts of accreting dark matter haloes exhibit a sudden drop in density delimiting their multistream region. Due to the dynamics of accretion, the location of this physically motivated edge strongly correlates with the halo growth rate. Using hydrodynamical zoom-in simulations of high-mass clusters, we explore this definition in realistic simulations and find an explicit connection between this feature in the dark matter and galaxy profiles. We also show that the depth of the splashback feature correlates well with the direction of filaments and, surprisingly, the orientation of the brightest cluster galaxy. Our findings suggest that galaxy profiles and weak-lensing masses can define an observationally viable mass-size scaling relation for galaxy clusters, which can be used to extract cosmological information.
Highlights
In the ΛCDM paradigm, structure in the Universe arises from the initial density perturbations of an homogeneous dark matter distribution
We find that the splashback feature seen in the galaxy, subhalo, and total matter profiles are all at the same location
Regarding the anisotropy in the splashback feature due to filamentary structures, we report that this phenomenon exists at high redshift
Summary
In the ΛCDM paradigm, structure in the Universe arises from the initial density perturbations of an (almost) homogeneous dark matter distribution. Some of the baryonic matter, following this process, cools down and settles at the centres of the gravitational potentials where it forms galaxies This mechanism has been studied through models of so-called spherical collapse (Gunn & Gott 1972; Bertschinger 1985), whose main prediction is the existence of a radius within which the material orbiting the halo is completely virialized. This virial radius depends on cosmology and redshift, but both in numerical simulations and observations, fixed overdensity radii are widely used as proxies for this quantity.
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