Collaborative Research: The Final Frontier: Spectroscopic Probes of Galaxies at the Epoch of Reionization

宇宙的黑暗时代（在第一颗恒星形成之前）被认为在大爆炸后大约5亿年结束，当时早期的光源产生了足够的高能光子来电离中性氢。这个时代被称为再电离。这是第一个星系形成的时候。但再电离到底是什么时候发生的，持续了多长时间？电离中性气体的来源是什么？是第一个星系还是黑洞的吸积？这个项目将通过使用世界上最好的望远镜来回答这些问题。观测将包括第一批星系的图像和光谱，这将使我们第一次看到这个重要星系群的化学成分。该项目还包括一个强有力的教育/公共宣传部分。为了帮助培养未来的科学家，PI将为K-12学生开发一门观察课程。PI和co-PI也在为非科学专业的学生开发课程。再电离时代标志着宇宙从不透明到透明的转变，但人们对它知之甚少。什么时候开始/结束的？是斑驳的还是光滑的？星系是如何使宇宙再电离的（如果是的话）？最早的星系有什么特性？为了回答这些问题，在过去的几十年里，一些调查已经在逐渐增加的深度上探索了高红移宇宙。然而，他们仍然缺乏样本大小或深度（或两者兼而有之）。从这些调查中得出的结论是，这些问题的答案很可能与更微弱星系的特性有关。这个项目将通过对红移z6的大量以前未探索过的微弱星系群进行光谱研究来解决这个问题。这将通过使用作为宇宙望远镜的星系团，以及从深度辅助成像和低分辨率光谱数据中预先选择来源来实现。该项目将(1)提供再电离的时间线，(2)确定第一个星系在这一过程中所起的确切作用，以及(3)对最早星系的恒星特性提供见解。该项目的教育/公共推广部分将包括为加州州立数学与科学暑期学校（COSMOS）开发一门观察课程，该课程面向K-12学生。此外，研究人员还为非理科专业的学生开设了新的大学课程，名为“加州物理学”和“可持续能源物理学”。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The cosmic Dark Ages (before the first stars formed) are thought to have ended around 500 million years after the Big Bang when early light sources produced enough energetic photons to ionize the neutral hydrogen. This era is referred to as reionization. It is when the first galaxies formed. But when exactly did reionization occur and how long did it last? What were the sources responsible for ionizing the neutral gas? Was it the first galaxies or accretion onto black holes? This project will answer these questions by using the best telescopes in the world. The observations will include images and spectra of the first galaxies, which enable a first glimpse of the chemical composition of this important population. The project also includes a strong educational/public outreach component. To help train tomorrow's scientists, the PI will develop an observing course intended for K-12 students. The PI and co-PI are also developing courses for non-science majors.The epoch of reionization, which signified the transformation of the universe from opaque to transparent, is poorly understood. When did it start/end? Was it patchy or smooth? How did galaxies reionize the universe (if they did)? What are the properties of the earliest galaxies? To answer these questions, over the last decades, several surveys have explored the high redshift universe at progressively increasing depth. However, they still either lack the sample size or depth (or both). What emerges from these surveys is that the answers to these questions are likely tied to the properties of even fainter galaxies. This project will address the problem by conducting a spectroscopic study of a large sample of previously unexplored faint galaxy populations at redshifts z 6. This will be achieved by using galaxy clusters that serve as cosmic telescopes and by pre-selecting sources from deep ancillary imaging and low-resolution spectroscopy data. This project will (1) provide the timeline of reionization, (2) identify the exact role first galaxies played in this process, and (3) give insight on the stellar properties of the earliest galaxies. The educational/public outreach component of this project will include developing an observing course for California State Summer School for Mathematics and Science (COSMOS), intended for K-12 students. In addition, the investigators are also developing new university courses entitled the "Physics of California'' and "The physics of sustainable energy'' for non- science majors.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.