Toward Understanding the High Redshift Lyman-Alpha Forest

该奖项是根据2009年《美国复苏和再投资法案》(公法111-5)资助的。格内丁将研究星系间气体是如何被新形成星系中的热恒星及其活动核电离的。他和他的团队将使用非常大的模拟来计算中性氢气的预期吸收线谱，我们看到的是在大爆炸后的第一个10-20亿年。为了做到这一点，他们将使用他们开发的新的近似值来跟踪来自星系的紫外线通过星际气体的传输，只要明亮类星体周围的电离区不重叠，这个近似值就是准确的。因此，辐射将与气体完全耦合，因此其压力可以驱动气体运动。将使用一种新的形式主义来添加小尺度的结构，这些结构太小，无法通过模拟来解决。这些合成光谱将与斯隆数字巡天的大型数据库中的类星体观测结果进行比较。格内丁博士将为模拟进行详细的收敛测试，并测试新的统计数据，以便将模型光谱与观察到的光谱进行比较。研究生将通过参与研究进行培训。格内丁博士将制作拟议中的模拟的可视化图像，并通过博物馆合作伙伴分发，其中包括芝加哥的阿德勒天文馆和纽约市的美国自然历史博物馆。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Dr. Gnedin will study how the intergalactic gas becomes ionized by hot stars in newly-formed galaxies, and by their active nuclei. He and his team will use very large simulations to calculate the expected absorption-line spectra from neutral hydrogen gas which we see as it was in the first 1-2 billion years after the Big Bang. To do this, they will follow the transfer of ultraviolet light from the galaxies through the intergalactic gas using a new approximation that they have developed, which is accurate as long as the ionized regions around bright quasars do not overlap. Thus the radiation will be fully coupled to the gas, so that its pressure can drive gas motions. Structures on small scales too small for the simulations to resolve will be added using a new formalism. The synthetic spectra will be compared to observations of quasars from the very large database of the Sloan Digital Sky Survey. Dr. Gnedin will make detailed tests of convergence for the simulations, and test new statistics for comparing the model spectra with those observed.A graduate student will be trained by participation in the research. Dr. Gnedin will produce visualizations of the proposed simulations, and distribute them via museum partners, including the Adler Planetarium in Chicago and the American Museum of Natural History in New York City.