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和他的团队将把对形成星系的气体的观测与对气体状态的理论和数值研究结合起来。星系间气体被来自短寿命大质量恒星和活跃星系核的紫外线电离，所以中性气体的数量告诉我们过去的恒星形成，以及位于星系中心并为活跃星系核提供能量的黑洞。当宇宙膨胀到现在大小的四分之一时，为了限制这种电离光，研究小组将检查这一时期类星体的光谱，并对它们发出的光中中性氢的深度吸收线进行普查。他们将利用更远的类星体的红外光谱来测量恒星内部产生的较重元素的吸收线，以检查这些元素从恒星产生并被抛入星系间气体的速度有多快。通过观察天空中附近的类星体对的光谱，研究小组将研究近类星体周围的气体，因为它吸收了较远物体的光。该团队将改进一维辐射传输代码CUBA，并向公众发布。这个代码将被用来追踪电离光子，当它们在宇宙模型中传播时，这些模型既跟随不可见的暗物质，也跟随气体，因为气体凝结成恒星形成的星系。这些计算还将考虑星系风在将恒星中形成的金属吹到星系间气体中的作用。一名研究生和一名博士后将通过参与研究而得到培训。团队成员希望指导本科生研究人员，并参加一个针对低收入家庭有才华的本科生的暑期项目。升级后的古巴代码将发布给天文社区，模拟运行的可视化将用于公众宣传。

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.