Charting the history of reionization with radio observations of the early universe

雅各布斯博士被授予美国国家科学基金会天文学和天体物理学博士后奖学金，在亚利桑那州立大学开展研究和教育项目。这项研究的目标是探测第一批恒星的证据，这些恒星被认为是在大爆炸后大约5亿年的某个时候诞生的。这些恒星发出强烈的辐射，燃烧了宇宙中无处不在的氢大气。由于氢占宇宙中正常物质的四分之三，这最后一个全球宇宙学过程支撑了我们对宇宙学和星系形成的大部分了解。然而，由于早期恒星的极端距离和亮度，在普通恒星的光线下观测这一时期对世界上最先进的望远镜来说是一个挑战。这项研究计划的目标是使用两个最近完成的射电望远镜探测和表征星系间氢电离前和电离期间的射电发射。探测和描述这个“宇宙黎明”的预测无线电信号被天文学界列为首要任务。这个项目还将支持一个学生志愿者团，他们将把一个便携式天文馆带到学校，并将直接参与开发博物馆和天文馆设施的元素。其中包括一个最先进的3D天文馆剧院，在最近建成的亚利桑那州立大学天文大楼。数字技术的最新进展使得建造非常大的天线阵列成为可能，这些天线阵列提供了必要的灵敏度，可以在宇宙只有300亿年的时候探测到来自氢的无线电发射。辐射的波长为21cm，通过宇宙膨胀被拉伸到1.5至3m的观测波长，这取决于观测的时间周期。默奇森宽场阵列（MWA）和探测再电离时代的精密阵列（PAPER）都被设计成以必要的灵敏度观察这些波长，并且在很大程度上由美国国家科学基金会资助，远离干扰人类无线电发射；MWA位于西澳大利亚，PAPER位于南非的卡鲁沙漠。利用这两台望远镜，雅各布斯博士将对早期宇宙中来自氢的辐射量进行深度统计测量。部分工作包括进行观测，测量和消除来自其他明亮天体的其他明亮干扰信号，并将这些新知识应用于建造能够直接成像早期宇宙的更大望远镜。这些对明亮干扰信号的测量将形成一幅实质性的、有趣的、令人信服的美丽的宇宙图像，并为作为项目一部分的学生团队制作的展览提供基础数据集。本科生团队将有两个目标：第一，提高天文学和科学教育本科生的保留率；第二，将天文馆表演带到传统上服务不足的学校和部落中心，这些学校和部落中心无法利用其他更昂贵的项目。

Dr. Jacobs is awarded an NSF Astronomy and Astrophysics Postdoctoral Fellowship to carry out a program of research and education at Arizona State University. The goal of the research is to detect evidence of the first stars, thought to be born sometime about 500 Million years after the Big Bang. These stars emitted intense radiation which burned away the universe's pervasive atmosphere of Hydrogen. As hydrogen accounts for three quarters of the normal matter in the universe, this last global cosmological process underpins much of what is known about cosmology and galaxy formation. However, observing this time period in ordinary star light challenges the world's premier telescopes due to the extreme distance and faintness of the early stars. The goal of this research program is to detect and characterize radio emission from intergalactic hydrogen before and during its ionization using two recently completed radio telescopes. Detecting and characterizing the predicted radio signature of this "Cosmic Dawn" was rated as a top priority by the astronomical community. This project will also support a student volunteer corps who will take a portable a planetarium to schools and who will be directly involved in developing elements for museum and planetarium facilities. These include a state of the art 3D planetarium theater, in the recently constructed Arizona State University astronomy building.Recent advances in digital technology allow the construction of very large arrays of antennae which provide the necessary sensitivity to detect radio emission from Hydrogen when the universe was only 300Mya old. Emitted at a wavelength of 21cm, the radiation is stretched by cosmological expansion to an observed wavelength of 1.5 to 3m depending on the time period under observation. Both the Murchison Widefield Array (MWA) and the Precision Array for Probing the Epoch of Reionization (PAPER) have been designed to observe these wavelengths at the necessary sensitivity and are constructed, in large part with funding from the National Science Foundation, far from interfering human radio emission; the MWA is in Western Australia and PAPER is in the Karoo desert of South Africa. Using both telescopes, Dr. Jacobs will compile a deep statistical measure of the amount of radiation coming from Hydrogen in the early universe. Portions of the work include performing observations, measuring and removing other bright interfering signals from other bright astronomical objects, and applying this new knowledge to building larger telescopes capable of directly imaging the early universe. These measurements of bright interfering signals will form a substantial, interesting, and compellingly beautiful image of the universe and provide a foundation data set for exhibits produced by the student corps created as a part of the project. The team of undergraduate students will have two goals: First to improve retention of astronomy and science education undergraduates and second to bring planetarium shows to traditionally underserved schools and tribal centers which cannot take advantage of other, more costly, programs.