Collaborative Research: The First Galaxies and their Stellar Populations

自适应网格细化宇宙辐射流体动力学模拟由这个小组首创，最近扩展到包括足够的物理和足够的分辨率来直接模拟III星族恒星形成的迷你晕对第一个星系的先前影响。这一技术进步发生的时候，正是地面和太空观测正在提供星系的天体物理数据的时候，这些星系的红移范围从6到8.5，这是以前无法想象的。这些观测结果表明，在亮度函数的亮端有实质性的演化，而在暗端有一个陡峭的斜率，这与高红移矮星主导再电离光子预算的观点一致。它们还揭示了在这个红移间隔内恒星种群的实质性演变。模拟能力的进步也正好赶上了美国国家科学基金会支持的第一台持续千万亿次超级计算机“蓝水”的开始运行。结合这些软件、硬件和先进的数据，该项目将模拟第一批星系在整个质量和光度范围内的形成和演化，并通过模拟图像和光谱将结果与数据进行比较。这将导致对星族III初始质量函数、反馈效应、超大质量黑洞的增长，甚至暗物质功率谱的推断，并对星系中气体的吸积速率施加重要的限制。模拟将改善电离辐射逃逸到星系间介质的估计，并直接解决高红移星系是否有能力再电离宇宙。由于千万亿次计算硬件、模拟软件和算法的进步，这是第一次这样的近第一原理模拟是可行的，也是第一次获得相关的观测约束。这种规模的模拟对天文社区、高性能计算社区和更大的对科学和技术好奇的公众产生了强烈的影响。它们推动硬件、软件和网络基础设施的开发。该项目是首批获得美国国家科学基金会新千万亿级超级计算机的六个项目之一，所需的代码增强将普遍可用。他们还计划在2013年由圣地亚哥巴尔博亚公园的鲁本·h·弗利特科学博物馆制作的一部新的IMAX电影中收录这些科学成果。

AST-1109243/1109008Norman/ReynoldsAdaptive mesh refinement cosmological radiation hydrodynamic simulations pioneered by this group have recently expanded to include sufficient physics and enough resolution to simulate directly the prior effects of Population III star-forming mini-halos on the first galaxies. This technical advance has occurred just when observations from both ground and space are providing astrophysical data on galaxies in the previously unimaginable range of redshifts from 6 to 8.5. These observations indicate substantial evolution in the bright end of the luminosity function, and a steep faint end slope consistent with the notion that high-redshift dwarfs dominate the reionization photon budget. They also reveal substantial evolution in stellar populations over this redshift interval. The advance in simulation capability is also well timed for the start of operations of the first NSF-supported sustained petaflops supercomputer, Blue Waters.Combining these software, hardware, and data advances, this project will simulate the formation and evolution of the first galaxies across the entire range of masses and luminosities observed, and compare the results to the data through simulated images and spectra. This will lead to inferences about the Population III initial mass function, feedback effects, the growth of supermassive black holes, and even the dark matter power spectrum, and place important constraints on the accretion rate of gas onto galaxies. The simulations will improve estimates of the escape of ionizing radiation into the intergalactic medium, and directly address whether high-redshift galaxies are capable of reionizing the Universe. This is the very first time such near-first-principles simulations are feasible, due to the convergence of petascale computing hardware, simulation software, and algorithmic advances, and also the first time that relevant observational constraints are being obtained.Simulations at this scale have a strong impact on the astronomical community, the high performance computing community, and the larger science and technology-curious public. They drive the development of the hardware, software, and networking infrastructure. This project is one of six selected for first access to NSF's new petascale supercomputer, and the required code enhancements will be made generally available. There are also plans to include these scientific results in a new IMAX film by the Reuben H.Fleet Science Museum in Balboa Park, San Diego, anticipated in 2013.