How Bright is the Radio Sky? A 310 MHz Absolute Map

观察宇宙中所有来自天文光源的光是很重要的，包括人类肉眼看不到的光，比如波长较长的无线电波。除了我们所知道的来自太空中明亮物体的无线电波外，还有来自天空各个方向的漫射无线电发射。这种漫射射电发射只能通过在天空的大部分地区以不同的射电波长进行观测来正确理解。该项目将利用罗伯特·c·伯德格林班克望远镜的独特功能，以及专门为该项目开发的先进定制仪器，绘制这些信号的新的现代地图。研究人员将利用尖端的无线电接收器技术和当代计算能力来实现前所未有的精度。由此产生的来自我们宇宙的射电发射图像将作为一种重要的资源提供给天文学界。该项目还将为研究人员和学生提供必要的直接培训机会。这个项目将产生一个新的310兆赫的绝对天空亮度图，其角度分辨率比银河特征和偏振信息更精细。由此产生的地图将是40年来第一个如此大规模、绝对校准的无线电地图，也是唯一一个以绝对零电平校准为主要目标的地图。这张赤纬-47度以北的整个天空的地图，加上观测到的所有银河系纬度，将使我们第一次以系统可靠的方式确定宇宙和银河系结构中漫射无线电发射的绝对水平。它将为理解和限制几乎所有银河系和星系外的现象提供一个重要的新资源，这些现象体现在或依赖于对漫射无线电发射的理解。这些研究包括宇宙微波背景研究、21厘米宇宙学、宇宙射线传播、磁场结构、超新星遗迹和脉冲星搜索、星际介质的组成、更精细的无线电结构、其他波长的银河系现象的示踪剂、无线电同步加速器背景的研究等等。研究人员将在格林班克望远镜上部署一个定制的、新型的偏振敏感接收器和低旁瓣、高边缘锥度馈电。将部署和表征的新型接收器技术有可能在射电天文学中产生重要应用。该项目将为博士后研究人员和本科生提供必要的直接培训，并为研究生提供许多潜在的研究机会，因为它将使各种各样的天体物理学研究成为可能。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。

It is important to observe all of the light that comes to us from astronomical sources in the universe, including the kinds of light that human eyes cannot see, like the longer wavelength of light called radio waves.  In addition to the radio waves that come from bright objects in space that we know about, there is also diffuse radio emission which comes from every direction in the sky.  This diffuse radio emission can only be properly understood by observing it over large portions of the sky at different radio wavelengths.  This project will make a new, modern map of these signals by utilizing the unique features of the Robert C. Byrd Green Bank Telescope along with advanced custom instrumentation developed specifically for this project.  The investigators will leverage cutting-edge radio receiver technology and contemporary computing capabilities to achieve unprecedented accuracy.  The resulting picture of the radio emission coming from our universe will be available to the astronomical community as an important resource. This project will also provide essential direct training opportunities for researchers and students. This project will produce a new map of the absolute sky brightness at 310 MHz, with angular resolution finer than Galactic features as well as polarization information. The resulting map will be the first such large-scale, absolutely calibrated radio map to be made in 40 years and the only one ever where an absolute zero-level calibration is the primary goal.  This map of the whole sky north of -47 degrees declination, with all Galactic latitudes observed, will allow a determination, for the first time in a systematically reliable way, of the absolute level of diffuse radio emission in the universe and from Galactic structure.  It will provide an important new resource for understanding and constraining almost all Galactic and extragalactic phenomena that manifest in, or depend on the understanding of, diffuse radio emission. These include cosmic microwave background studies, 21-cm cosmology, cosmic ray propagation, magnetic field structures, supernova remnant and pulsar searches, composition of the interstellar medium, finer scale radio structure, tracers for Galactic phenomena at other wavelengths, investigations of the radio synchrotron background, and many more.  The investigators will deploy a custom, novel polarization-sensitive receiver and low sidelobe, high edge-taper feed on the Green Bank Telescope.  The novel receiver technologies that will be deployed and characterized have the potential to yield important applications in radio astronomy.  This project will provide essential direct training for postdoctoral researchers and undergraduate students, as well as many potential research opportunities for graduate students given the wide variety of astrophysical investigations it will enable.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.