The Mass of Virialized Dark Matter Haloes

TL;DR

This paper proposes a new method for estimating dark matter halo mass by analyzing the stationary region with zero mean radial velocity in cosmological simulations, improving upon traditional virial mass estimates.

Contribution

It introduces a novel approach to define halo mass based on the stationary region with zero mean radial velocity, better reflecting the halo's dynamical structure.

Findings

The stationary region provides a more accurate mass estimate.

Traditional overdensity criteria do not align with the dynamical structure.

Simulation analysis supports the new mass estimation method.

Abstract

Virial mass is used as an estimator for the mass of a dark matter halo. However, the commonly used constant overdensity criterion does not reflect the dynamical structure of haloes. Here we analyze dark matter cosmological simulations in order to obtain properties of haloes of different masses focusing on the size of the region with zero mean radial velocity. Dark matter inside this region is stationary, and thus the mass of this region is a much better approximation for the virial mass.