MultiDark simulations: the story of dark matter halo concentrations and density profiles.
Anatoly Klypin1 and Et Al3,4 1Astronomy Department, New Mexico State University, Las Cruces, NM, USA Anatoly Klypin1, Gustavo Yepes2, Stefan Gottlöber3, Francisco Prada4,5,6, and Steffen Heß3 1 Astronomy Department, New Mexico State University, Las Cruces, NM, USA 2 Departamento de Física Teórica M8, Universidad Autonoma de Madrid (UAM), Cantoblanco, E-28049, Madrid, Spain 3 Leibniz-Institut für Astrophysik Potsdam (AIP), Potsdam, Germany 4 Instituto de Física Teórica, (UAM/CSIC), Universidad Autónoma de Madrid, Cantoblanco, E-28049 Madrid, Spain 5 Campus of International Excellence UAM+CSIC, Cantoblanco, E-28049 Madrid, Spain 6 Instituto de Astrofísica de Andalucía (CSIC), Glorieta de la Astronomía, E-18080 Granada, Spain E-mail:
Abstract
Predicting structural properties of dark matter halos is one of the fundamental goals of modern cosmology. We use the suite of MultiDark cosmological simulations to study the evolution of dark matter halo density profiles, concentrations, and velocity anisotropies. We find that in order to understand the structure of dark matter halos and to make 1–2% accurate predictions for density profiles, one needs to realize that halo concentration is more complex than the ratio of the virial radius to the core radius in the Navarro-Frenk-White profile. For massive halos the average density profile is far from the NFW shape and the concentration is defined by both the core radius and the shape parameter $\alpha$ in the Einasto approximation. We show that halos progress through three stages of evolution. They start as rare density peaks and experience fast and nearly radial infall that brings mass closer to the center, producing a highly concentrated halo. Here the halo concentration increases with increasing halo mass and the concentration is defined by the $\alpha$ parameter with a nearly constant core radius. Later halos slide into the plateau regime where the accretion becomes less radial,
中文速览
暗物质晕（dark matter halo）的密度分布和集中度（concentration）是宇宙学模型预测的核心参数，但学界对集中度随质量变化的三种行为——上升、平坦、下降——长期存在争议。研究者利用 MultiDark 系列宇宙学模拟，系统追踪了不同质量和红移下暗物质晕的密度剖面、集中度及速度各向异性的演化，发现暗物质晕依次经历三个阶段：早期作为高峰度密度扰动快速近径向吸积，集中度随质量增大而升高；随后进入平台阶段，频繁并合使集中度不随质量变化；最终进入慢速吸积阶段，新落入物质堆积在外围，核心半径基本不变，集中度随质量增大而下降。研究还指出，对大质量晕而言，NFW 剖面已不够准确，必须引入 Einasto 剖面的形状参数 α 才能实现 1–2% 精度的密度剖面预测，而以往方法之间看似矛盾的集中度估计，实则是因为各方法度量的是不同物理量。这一成果为即将到来的大规模星系巡天提供了高精度的暗物质晕结构解析框架。
原文 arXiv:1411.4001;中英对照 + 大白话阅读 https://aha.fim.ai/paper/1411.4001v2