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

星际介质(IGM)是弥漫在星系之间的炽热的X射线气体。目前，标准的数值模拟不能与IGM的几个关键观测特征相匹配。模拟数据和观测数据之间的不匹配太大了，不是由观测误差造成的，而且在使用不同统计数据的多次比较中可以看到，而且是由不同的组进行的。该项目建议通过在Blue Waters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一悬而未决的问题，以对IGM做出更准确和更可靠的估计。此外，这些模拟和代码将公开提供，以允许其他人根据现有的或新的观测数据做出自己的估计。该项目将使用新开发的Enzo极端尺度分支Enzo-P来模拟氢莱曼阿尔法森林(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，其基础是名为Cello的新的高度可扩展的AMR基础设施。恩佐-P和大提琴都是由加州大学圣迭戈分校的PIS小组开发的。Enzo-P和Cello的结合将首次允许在大宇宙体积中使用AMR，消除了以前Enzo模拟所特有的大体积统计和高局部分辨率之间的现有权衡。该项目将应用这一新能力，以足够高的分辨率对LAF进行模拟，以捕获对银河系间吸收有重大贡献的星系的气态晕，同时测量具有统计意义的宇宙体积。此外，该项目将构建合成的LYAF光谱并分析其统计特性，以查看模型中包含的高柱密度吸收体是否改善了协议观察。该奖项反映了NSF的法定使命，并已通过使用基金会的智力优势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.