On the Kinematic Morphology around Halos

TL;DR

This paper investigates the kinematic flow morphologies around dark matter halos, revealing a sharp transition at the splashback radius that encodes phase space information and enhances understanding of halo dynamics.

Contribution

It introduces a new kinematic perspective on flow morphologies around halos, highlighting a sharp feature at the splashback radius linked to phase space structure.

Findings

Flow morphology profiles exhibit a sharp change at the splashback radius.

Spiral inward flow concentrates around halos and relates to large-scale structure.

Rotational flow morphologies reveal anisotropic phase structures.

Abstract

In this paper, we report an interesting kinematic phenomenon around the halos' edge related to the splashback radius. After the shell-crossing, cosmic flow exhibits various rotational morphologies via stream-mixing. Vorticity is generated in a particular way that coincides with the large-scale structure. Notably, one specific flow morphology, which is spiraling inward and compressing in the third direction, concentrates around halos. A detailed examination that reveals a sharp change in the logarithmic derivative of its volume fraction, coincides with the location of the splashback radius defined as the outermost caustic structure. Such a feature encodes valuable phase space information and provides a new perspective on understanding the dynamical evolution of halos. As a volume-weighted quantity, the profile of flow morphology is purely kinematic. And unlike other related studies, the rotational flow morphologies capture the anisotropic phase structure in the multi-stream region.