Realistic simulations of the intergalactic medium CDS&E

令人惊讶的是，人们对填充星系间广阔空间的物质（星系间介质，简称IGM）知之甚少。研究IGM的一个主要方法是通过它从非常遥远的非常明亮的类恒星物体（类星体）吸收的光，类星体在非常特定的波长上显示出数百种可测量的特征。不幸的是，详细的计算工作仍然无法重现IGM的关键方面，所有这些都是在同一时间使用相同的输入参数。这一定意味着这些模拟不能正确地代表真实的宇宙。本研究试图通过对数值研究中包含的物理进行系统的研究，并对待研究的大参数空间的有效区域进行严格的描述，来纠正这一失败。IGM在类星体光谱中产生了数百条吸收线，这些吸收线对宇宙的热历史很敏感，但是，正如前面提到的，目前的数值模拟不能同时匹配几个关键特征。这种差异太大，不可能是由于观测误差造成的，即使使用不同的数值方法，也可以在多次比较中看到。这个研究小组有几十年观察IGM和运行高保真度模拟的经验，并被迫得出结论，模拟根本不能正确地代表我们的宇宙。因此，该项目将通过四种新型模拟，包括新的辐射输运求解器、具有参数化反馈的高分辨率大盒模拟、首次具有自洽三维辐射传输的IGM模拟，以及探索各种其他可能热源的物理动机模拟，来寻找IGM的真实表现。所有这些结果将被综合，精确地参数化它们如何改变IGM的外观，以便选择那些将忠实地生成IGM观测值的参数值。这项工作应该找到我们对IGM的理解中缺失的东西，并发现和指定可以精确再现IGM中主要物理过程的模拟。它将导致对IGM温度、密度和电离、紫外线背景辐射强度以及用于设定中微子质量限制的小尺度物质聚集的更准确和可靠的估计。所有的模拟和生成代码都是公开的。这个团队在将教育和多样性融入他们的核心研究方面有20年的记录。本科生将接受宇宙学、天体物理学、光谱学和模拟方面的指导，他们将使用先进的软件工具。

The material that fills the vast spaces between galaxies (the Intergalactic Medium, or IGM) is surprisingly poorly understood. One primary method of investigating the IGM is through the light it absorbs from very distant very bright quasi-stellar objects (quasars), which show hundreds of measurable features at very specific wavelengths. Unfortunately, detailed computational work is still unable to reproduce key aspects of the IGM, all at the same time and using the same input parameters. This must mean that those simulations do not correctly represent the real Universe. This study attempts to correct this failing with a systematic investigation of the physics included in the numerical studies, and a rigorous delineation of the valid regions of the large parameter space to be investigated.The IGM makes hundreds of absorption lines in quasar spectra that are sensitive to the thermal history of the Universe, but, as noted, current numerical simulations cannot simultaneously match several key features. The discrepancy is too large to be due to observational errors, and is seen in multiple comparisons even when using different numerical methods. This research team has decades of experience observing the IGM and running high fidelity simulations, and is forced to conclude that the simulations simply do not correctly represent our Universe. Therefore, this project will search for a realistic representation of the IGM through four new types of simulation, including a new radiation transport solver, a high resolution large box simulation with parameterized feedback, the first ever simulation of the IGM with self-consistent 3D radiative transfer, and physically motivated simulations that explore a wide variety of other possible heat sources. All these results will be synthesized, parameterizing precisely how they change the appearance of the IGM, so as to select those parameter values that will faithfully generate observations of the IGM. The work should locate what is missing from our understanding of the IGM, and discover and specify simulations that can exactly reproduce the main physical processes in the IGM. It will lead to more accurate and robust estimates of the IGM temperature, density and ionization, the intensity of the ultraviolet background radiation, and the clustering of matter on small scales that is used to set limits on neutrino masses. All of the simulations and the generating codes will be publicly available. This team has a two decade record of integrating education and diversity into their core research. Undergraduate students will receive instruction in cosmology, astrophysics, spectroscopy, and simulations, and they will work with advanced software tools.