Realistic Simulations of the Intergalactic Medium: The Search for Missing Physics - Part 2

星系间介质（IGM）是一种散发x射线的热气体，它渗透在星系间的空间中。目前，标准数值模拟无法匹配IGM的几个关键观测特征。模拟和观测数据之间的不匹配太大，不可能是由观测误差引起的，并且在使用不同统计数据和不同组的多次比较中可以看到。这个项目提议通过在蓝水超级计算机上运行非常高分辨率的模拟来解决天体物理学中的这个开放问题，从而对IGM做出更准确和可靠的估计。此外，模拟和代码将公开，以允许其他人根据现有或新的观测结果做出自己的估计。该项目将使用新开发的Enzo极端尺度分支Enzo- p来模拟氢莱曼α森林（LYAF）。Enzo- p从广泛使用的Enzo社区代码中实现了丰富的物理模型套件，这些物理模型位于一个名为Cello的新的高度可扩展的AMR基础设施之上。Enzo-P和Cello都是由加州大学圣地亚哥分校的pi小组开发的。Enzo- p和Cello的结合将首次允许在大的宇宙体积中使用AMR，消除了以前Enzo模拟中存在的大体积统计和高局部分辨率之间的权衡。该项目将应用这种新能力，以足够高的分辨率对LAF进行模拟，以捕捉对星系间吸收有重大贡献的星系的气体晕，同时测量宇宙的统计显著体积。此外，该项目将构建合成LYAF光谱并分析其统计特性，以确定模型中包含高柱密度吸收剂是否改善了一致性观测。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The intergalactic medium (IGM) is the hot, X-ray emitting gas that permeates the space between galaxies. Currently, standard numerical simulation cannot match several key observational features of the IGM. The mismatch between the simulations and observation data is much too large to be caused by observational errors, and is seen in multiple comparisons using different statistics, and by different groups. This project proposes to resolve this open question in astrophysics by running very high resolution simulations on the Blue Waters supercomputer to make more accurate and robust estimates of the IGM. Furthermore, the simulations and codes will be publicly available to allow others to make their own estimates from existing or new observations.The project will simulate the hydrogen Lyman alpha forest (LYAF) using the newly developed extreme scale branch of the Enzo called Enzo-P. Enzo-P implements the rich suite of physics models from the widely used Enzo community code on top of a new, highly scalable AMR infrastructure called Cello. Both Enzo-P and Cello have been developed by the PIs group at UCSD. The combination of Enzo-P and Cello will permit for the first time the use of AMR throughout a large cosmological volume, removing the existing tradeoff between large volume statistics and high local resolution that characterized previous Enzo simulations. The project will apply this new capability to carry out simulations of the LAF with sufficiently high resolution to capture the gaseous halos of galaxies which contribute significantly to intergalactic absorption, while at the same time surveying a statistically significant volume of the universe. Moreover, the project will construct synthetic LYAF spectra and analyze their statistical properties to see whether the inclusion of high column density absorbers in the model improves agreement observations.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.