Collaborative Research: Cosmology with CHIME

加拿大氢强度测绘实验（CHIME）将通过绘制宇宙中物质的分布来帮助理解暗能量。科学上最大的谜团之一是宇宙的膨胀目前正在加速，这意味着一种神秘的暗能量渗透到宇宙中并推动着它。暗能量的发现获得了诺贝尔奖，但它的本质在今天并不像20年前那样清晰。事实上，最近的测量结果对宇宙膨胀的确切速度进行了不同的测量，结果不太确定。CHIME是一种新型射电望远镜，旨在通过射电发射存在于其中的中性氢气来测量遥远的星系。为了测量氢的发射，来自我们银河系和其他来源的其他明亮的无线电信号必须被移除。这种前景移除需要对CHIME仪器本身有精确的了解。该项目将测量该仪器，改进干扰无线电发射的去除，并将CHIME测量与星系目录相结合，以测量暗能量。该项目还将开发面向教育的无线电接收器，用于麻省理工学院、西弗吉尼亚大学和耶鲁大学的STEM项目。WVU和格林班克天文台合作开发了教育用无线电接收机，向教师传授建立数字光谱仪所需的数字信号处理技术。将CHIME的21厘米地图与eBOSS的光学星系调查数据进行交叉相关分析，以测量宇宙的大尺度结构（LSS）。CHIME设计用于测量与星系相关的中性氢，红移范围从0.8到2.5，在一个关键的红移范围内产生暗能量的限制，仅凭光学星系调查很难进行统计探测。为了进行这项测量，我们必须去除来自银河系和银河系外的明亮前景辐射，这对仪器校准提出了严格的要求。在这个项目中，研究人员将尝试通过以下方法来测量膨胀历史：(i)改进的仪器光束建模，（ii）演示前景去除技术，以及（iii）测量与eBOSS光学星系相互关联的21cm发射的大尺度结构。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 Canadian Hydrogen Intensity Mapping Experiment (CHIME) will help understand dark energy by mapping out the distribution of matter throughout the Universe. One of the greatest mysteries in science is that the expansion of the Universe is currently accelerating, implying that a mysterious dark energy permeates the Universe and pushes on it. The discovery of dark energy resulted in a Nobel Prize, but its nature is no clearer today than it was 20 years ago. In fact, more recent measurements have led to less certainty, with different measurements of exactly how fast the Universe is expanding. CHIME is a new radio telescope designed to measure distant galaxies through the radio emission of neutral hydrogen gas that resides within them. In order to measure the hydrogen emission, other bright radio signals from our own galaxy and other sources must be removed. This foreground removal requires a precise understanding of the CHIME instrument itself. This project will measure the instrument, improve nuisance radio emission removal, and combine the CHIME measurements with galaxy catalogues to make a measurement of dark energy. The program will also develop education-oriented radio receivers that will be used in STEM programs at MIT, WVU and Yale. Radio receivers for education have been developed through a partnership between WVU and the Green Bank Observatory to teach teachers the digital signal processing techniques necessary to build a digital spectrometer.Analysis will be undertaken that cross-correlates 21cm maps from CHIME with optical galaxy survey data from eBOSS to measure the large-scale structure (LSS) of the Universe. CHIME is designed to measure neutral hydrogen associated with galaxies at redshifts from 0.8 to 2.5, producing constraints on dark energy over a critical redshift range that is difficult to probe statistically with optical galaxy surveys alone. To make this measurement bright foreground emission from our own galaxy and extragalactic sources must be removed, which places stringent requirements on instrument calibration. In this program the researchers will attempt to measure the expansion history through: (i) improved instrument beam modelling, (ii) demonstrated foreground removal techniques, and (iii) the measurement of large-scale structure with 21cm emission in cross-correlation with eBOSS optical galaxies.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.