Speaker
Description
We investigate the splashback features of nonspherical dark-matter halos in phase space, namely based on cosmic density and velocity fields. Besides the density correlation function binned by the halo orientation angle, which was used in the literature, we introduce the corresponding velocity statistic, alignment velocity correlation function, to consider halo's asphericity. Using large-volume, high-resolution $N$-body simulations, we measure the density and velocity alignment statistics. On halo scales, $\sim 1 h^{-1} {\rm mpc}$, we detect a sharp steepening in the velocity correlation associated with the physical halo boundary, or the splashback feature, which is found more prominent than in the density correlation. We also find that the splashback radius determined from the density correlation becomes $\sim 3.5\%$ smaller than that from the momentum correlation. Moreover, the orientation-dependent splashback feature due to halo asphericity is measured when the density profile is determined by dark-matter particles, which can be used as a test of collisional cold dark matter since the halo shape is predicted to be rounder in such a model.
