Collaborative Research: Modelling the Turbulent Galaxy Formation

任何有流体在运动的地方，无论是液体还是气体，都会有湍流。这些对宇宙流动的扰动可能是非常重要的，但它们可能对宇宙气体形成星系的深远影响仍然是我们对宇宙如何演化的基本理解中的一个谜团。这项工作试图纠正这一缺陷，使用高性能计算机进行非常高分辨率的新颖数值模拟。这是第一次，几乎所有涉及星系内恒星形成的物理学都将被包括在内。这些计算将与望远镜数据密切相关，既检查计算机结果，又帮助理解观测结果。这些新想法也将有助于对湍流的其他研究。宇宙气体流动速度快，跨越巨大的尺度，具有高度的湍流，但湍流对星系形成可能产生的深远影响在很大程度上尚不清楚。这个项目是在使用自适应网格加密(AMR)的自洽宇宙学模拟中，系统地探索湍流及其对吸积流、恒星形成和星系结构的影响。部分工作将实施和测试一个新的亚网格尺度湍流模型，并用它来估计局部湍流应力。这个模型将被用来在星系形成模拟中加入新的物理驱动的恒星形成处方，纳入了一套被认为对与观测进行比较至关重要的丰富的物理过程，包括分子氢的建模、化学浓缩和演化、尘埃的形成和破坏、电离和远紫外线的辐射传输、恒星形成以及恒星与辐射压力和宇宙射线的反馈。观测比较将检验和告知理论模型，而模拟结果将有助于理解数据。科学成果将包括量化湍流对星系冷吸积气体流动的影响，评估湍流动力驱动的相对贡献，以及量化湍流对气体密度结构的影响。对观测比较的重视将使这项研究对解释现有和未来设施的结果特别有价值。这些方法和结果对其他模拟和半解析模型都有一定的参考价值。这些模拟还可以很好地实现高保真、科学准确的可视化，非常适合全穹顶天文馆投影仪的高分辨率环境，但对所有天文馆都有价值。

Anywhere that there is a fluid in motion, whether liquid or gas, there will be turbulence. These disturbances to the flow can be very significant, but their possibly profound effect on the formation of galaxies out of the cosmic gas remains an area of mystery in our fundamental understanding of how the Universe evolves. This work seeks to correct this lack, using high powered computers to carry out novel numerical simulations with very high resolution. For the first time, pretty well all of the physics involved in forming stars within galaxies will be included. The calculations will be intimately connected with telescope data, both checking the computer results and helping to understand the observations. The new ideas will also be useful for other studies of turbulent fluids.Cosmic gas flows have high velocities, span enormous scales, and are highly turbulent, but the possibly profound effects of turbulence on galaxy formation are largely unexplored. This project is a systematic exploration of turbulence and its effects on accretion flows, star formation, and the structure of galaxies, in self-consistent cosmological simulations using adaptive mesh refinement (AMR). Part of the work will implement and test a novel model for sub-grid scale turbulence and use it to estimate local turbulent stresses. This model will be used to add new physically-motivated prescriptions for star formation into the galaxy formation simulations, incorporating a rich set of physical processes thought to be critical for comparison with observations, including modeling of molecular hydrogen, chemical enrichment and evolution, dust formation and destruction, radiative transfer of ionizing and far-ultraviolet radiation, star formation, and stellar feedback with radiation pressure and cosmic rays. Observational comparisons will test and inform the theoretical models, while the simulation results will help to understand the data. Scientific results will include quantifying the effects of turbulence on the cold accretion gas flows onto galaxies, assessing the relative contribution of dynamical drivers of turbulence, and quantifying the effects of turbulence on the density structure of the gas. The emphasis on observational comparisons will make this study particularly valuable for interpreting the results from current and future facilities. Both the methods and the results will be of value for other simulations and for semi-analytic models. The simulations also lend themselves well to high-fidelity, scientifically-accurate visualizations well suited to the high resolution environment of full-dome planetarium projectors, but of value to all planetaria.