The Imprint of Galaxy Formation on the Intergalactic Environment

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。Madau博士和他的团队将把对星系形成气体的联合收割机观测与对该气体状态的理论和数值研究结合起来。 星系际气体被来自短寿命大质量恒星和星系活动核的紫外线电离，因此中性气体的数量告诉我们过去星星的形成，以及位于星系中心并为其活动核提供动力的黑洞。 为了在宇宙只膨胀到目前大小的四分之一时限制这种电离光，研究小组将检查这一时期类星体的光谱，并对它们光中中性氢的深吸收线进行普查。 他们将利用更遥远的类星体的红外光谱来测量恒星内部产生的重元素的吸收线，以研究这些元素从恒星产生并被抛入星系际气体的速度。 通过观察天空中邻近的类星体对的光谱，研究小组将通过吸收更遥远物体的光来研究更近的类星体周围的气体。 该团队将改进CUBA，一个一维辐射传输代码，并向公众发布。 这个代码将被用来追踪电离光子，因为它们在宇宙模型中传播，这些模型既遵循不可见的暗物质，也遵循气体，因为气体凝结成恒星形成星系。 这些计算还将考虑星系风将恒星中形成的金属吹到星系际气体中的影响。 一名研究生和一名博士后将通过参与研究进行培训。 团队成员希望指导本科研究人员，并参加一个夏季计划，为有才华的本科生从低收入家庭。 升级后的CUBA代码将向天文学界发布，模拟运行的可视化结果将供公众使用。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Dr. Madau and his team will combine observations of the gas from which the galaxies were formed with theoretical and numerical studies of the state of that gas. The intergalactic gas is ionized by the ultraviolet light from short-lived massive stars and from the active nuclei of galaxies, so the amount of neutral gas tells us about past star formation, and about the black holes that lie at the centers of galaxies and power their active nuclei. To set limits on this ionizing light at times when the cosmos had expanded only to a quarter of its present size, the team will examine the spectra of quasars dating from this period, and make a census of the deep absorption lines of neutral hydrogen in their light. They will take infrared spectra of even more distant quasars to measure the absorption lines of heavier elements that are produced in stellar interiors, to examine how rapidly these were produced from stars and flung into the intergalactic gas. By looking at spectra of pairs of quasars that are nearby on the sky, the team will study gas around the nearer quasar by its absorption of the light of the more distant object. The team will improve CUBA, a one-dimensional radiative transfer code, and release it to the public. This code will be used to trace ionizing photons as they propagate through models of the cosmos that follow both the invisible dark matter and the gas, as gas condenses into star-forming galaxies. These calculations will also consider the effect of galactic winds in blowing the metals formed in the stars out into the intergalactic gas. A graduate student and a postdoc will be trained by participating in the research. Team members expect to mentor undergraduate researchers, and to take part in a summer program for talented undergraduates from low-income families. The upgraded CUBA code will be released to the astronomical community, and visualizations from the simulation runs will be available for public outreach.