Realistic Simulations of the Intergalactic Medium: The Search for Missing Physics

星际介质的真实模拟：寻找缺失的物理现象

• 批准号: 1516003
• 负责人: Michael Norman
• 金额: $ 1.05万
• 依托单位: University of California-San Diego
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-08-01 至 2018-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1516003&HistoricalAwards=false
• 关键词: Realistic; Simulations; Intergalactic; Medium; Search

In the past decade new, more precise observations of the intergalactic medium (IGM)--the hydrogen and helium gas between the galaxies produced in the Big Bang--have revealed a discrepancy with the well-established predictions of our computational models. In particular, precision observations of the IGM using the Keck telescopes in Hawaii show that the temperature and ionization state of the IGM is not what our standard cosmological simulations predict: the IGM is either somewhat hotter than ultraviolet radiation from stars in galaxies can make it, or the IGM is distributed differently in space than the simulations predict, or both. There could be missing sources of heat in our models, such as energy injection by decaying dark matter particles. The discrepancy is perplexing since the standard model predicts the galaxy distribution exceedingly well. The discrepancy suggests that the standard model lacks some essential ingredient which we refer to simply as "missing physics". The significance of this project to the nation is that it promotes the progress of science in the fundamental field of cosmology where the US is a world leader. The project is addressing the issue of whether we are overlooking a key component of the mass-energy content of the universe. Precise answers require powerful tools, and the Blue Waters supercomputer is the tool for the job. In this work, the investigators will systematically explore how the discrepancy between models and observations can be removed. They will carry out on the Blue Waters supercomputer simulations of unprecedented size and physical realism to hunt down what the missing physics is. Since the IGM comprises most of the volume and matter in the universe, a small discrepancy may translate into a big discovery. Very large 3D simulations are required because the range of scales in each dimension exceeds 4000:1. They will examine whether additional heating sources such as X-rays and ultraviolet light from early galaxies and quasars can make up the heat deficit. Alternatively, they will also examine whether the limited spatial resolution in current simulations explains the discrepancy by carrying out the first large-scale simulations of the IGM that also simulates the gas near to galaxies in detail.

在过去的十年中，新的，更精确的观察结果是对星际培养基（IGM）的 - 大爆炸中产生的星系之间的氢气和氦气 - 揭示了对我们计算模型的完善预测的差异。特别是，使用夏威夷的KECK望远镜对IGM进行精确观察表明，IGM的温度和电离状态不是我们的标准宇宙学模拟预测的：IGM要么比星系中的星星从星星中的紫外线辐射更热，要么在空间中分布在空间上，或者在仿真中分配了不同的仿真，或者是两者的分布。在我们的模型中可能缺少热量来源，例如通过腐烂的暗物质颗粒注入能量。由于标准模型预测星系分布非常好，因此差异令人困惑。 差异表明，标准模型缺乏一些基本要素，我们将其简单地称为“缺失物理学”。该项目对国家的重要性是，它在美国是世界领导者的宇宙学基本领域中促进了科学的进步。该项目正在解决我们是否忽略宇宙质量能量内容的关键组成部分的问题。精确的答案需要强大的工具，而蓝色水域超级计算机是工作的工具。在这项工作中，研究人员将系统地探讨如何消除模型和观察之间的差异。他们将在蓝色水域超级计算机模拟上进行前所未有的大小和物理现实主义，以追捕失踪物理的含义。由于IGM包括宇宙中的大部分卷和物质，因此很小的差异可能转化为一个很大的发现。需要非常大的3D模拟，因为每个维度的尺度范围超过4000：1。他们将检查早期星系和类星体的其他加热源（例如X射线和紫外线）是否可以弥补热量不足。另外，他们还将检查当前模拟中有限的空间分辨率是否通过进行IGM的第一个大规模模拟来解释差异，该模拟还可以详细地模拟气体附近的气体。