Dependence of the dynamical properties of light-cone simulation dark matter halos on their environment

Abstract

Aims. To study the dependence of the dynamical properties of dark matter halos on their environment in a whole-sky ΛCDM light-cone simulation extending to z ∼ 0.65. The properties of interest are halo shape (parametrized by its principal axes), spin and virialisation status, the alignment of halo spin and shape, as well as the shape-shape and spin-spin alignments among halo neighbours. Methods. We define the halo environment using the notion of halo isolation status determined by the distance to its nearest neighbor. This defines a maximum spherical region around each halo devoid of other halos, above the catalog threshold mass. We consider as 'close halo pairs', the pairs that are separated by a distance lower than a specific threshold. In order to decontaminate our results from the known dependence of halo dynamical properties on mass, we use a random sampling procedure in order to compare properties of similar halo abundance distributions. Results. (a) We find a strong dependence of halo properties on their environment, confirming that isolated halos are more aspherical and more prolate with lower spin values. (b) Correlations between halo properties exist and are mostly independent of halo environment. (c) Halo spins are aligned with the minor axis, regardless of halo shape. (d) Close halo neighbors have their major axes statistically aligned, while they show a slight but statistically significant preference for anti-parallel spin directions. The latter result is enhanced for the case of close halo pairs in low-density environments. Furthermore, we find a preference of the spin vectors to be oriented perpendicular to the line connecting such close halo pairs.

Halo cluster shapes: Insights from simulated galaxies and ICL with prospects for weak lensing applications

“…Here we present the general trends obtained for the shapes of the DM and stellar distribution components. Overall, these results are in agreement with previous studies based on numerical simulations (e.g., Velliscig et al 2015;Vega-Ferrero et al 2017;Despali et al 2017;Chira et al 2020). We briefly comment our general results, and provide a more detailed analysis as complementary material in Appendices C and D. According to our analysis, and in agreement with previous studies including baryon physics, the DM distribution of galaxy clusters is rounder at the inner radii, both in 3D and in 2D projections.…”