Collaborative Research: Modelling the Turbulent Galaxy Formation

任何有流体运动的地方，无论是液体还是气体，都会有湍流。这些对气流的干扰可能是非常重要的，但它们对宇宙气体中星系形成的可能产生的深远影响，在我们对宇宙如何演化的基本理解中仍然是一个谜。这项工作试图纠正这一不足，使用高性能计算机进行具有非常高分辨率的新颖数值模拟。这是第一次，星系中形成恒星的所有物理过程都将被包括在内。计算将与望远镜数据密切相关，既可以检查计算机结果，也可以帮助理解观测结果。这些新想法也将对紊流的其他研究有用。宇宙气体流动速度快，跨度大，而且非常湍流，但是湍流对星系形成可能产生的深远影响在很大程度上尚未被探索。这个项目是一个系统的探索湍流及其对吸积流，恒星形成和星系结构的影响，在自洽宇宙学模拟中使用自适应网格细化（AMR）。部分工作将实现和测试一种新的亚网格尺度湍流模型，并用它来估计局部湍流应力。该模型将用于在星系形成模拟中添加新的恒星形成的物理驱动处方，将一套丰富的物理过程与观测结果进行比较，包括分子氢的建模，化学富集和演化，尘埃形成和破坏，电离和远紫外线辐射的辐射转移，恒星形成，以及辐射压力和宇宙射线的恒星反馈。观测比较将检验理论模型并为其提供信息，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冷吸积气体流向星系的影响，评估湍流动力驱动因素的相对贡献，以及量化湍流对气体密度结构的影响。对观察比较的强调将使本研究对解释当前和未来设施的结果特别有价值。本文的方法和结果对其它模拟和半解析模型具有一定的参考价值。模拟还可以很好地实现高保真度，科学精确的可视化，非常适合全圆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.