EDGES-2: Detecting First Light and Reionization through the Global 21 cm Signature

EDGES-2：通过全局 21 厘米特征检测第一光和再电离

• 批准号: 1207761
• 负责人: Judd Bowman
• 金额: $ 84.21万
• 依托单位: Arizona State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-06-01 至 2016-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1207761&HistoricalAwards=false
• 关键词: EDGES; Detecting; First; Light; Reionization

The formation of the first stars, galaxies, and black holes during what is known as the Cosmic Dawn is the next frontier in observational cosmology. During this epoch, the intergalactic medium (IGM) was primarily in the form of neutral hydrogen gas, accessible to observations through its redshifted 21 cm line. Once the first stars formed at a redshift z ~ 30, they produced a background of Lyman-alpha photons that coupled the neutral hydrogen spin temperature to the physical gas temperature in the IGM. This is thought to have caused the 21 cm line to become visible in absorption against the cosmic microwave background (CMB). Later, X-rays traveling long distances deposited their energy as heat and raised the IGM temperature. This heating drove the average 21 cm signal to rise into emission above the CMB, until the neutral gas was eventually ionized during the epoch of reionization, and no detectable signal remained. The evolution of these absorption and emission features in the early IGM should be evident in cosmic radio spectrum, since redshift maps to frequency for the 21 cm line. Significant observational challenges must be addressed to separate the expected 10-100 mK high-redshift 21 cm signal from the dominant Galactic foreground emission, but Dr. Judd Bowman of the Arizona State University and his collaborators at the Massachusetts Institute of Technology propose to overcome these challenges with a spectrometer featuring 10 times improved performance and frequency coverage from 40 to 200 MHz to span the redshift range 6 z 30. The new instrument, called EDGES-2, will make use of a new precision calibration method based on a generalization of the classic noise wave propagation model. Broader impacts of the project include demonstration of this new, high-precision calibration method for wideband systems, which has applications outside of radio astronomy, including to ionospheric study. The project also has a strong focus on providing opportunities for undergraduate and graduate student training and mentoring in an interdisciplinary environment to learn basic principles of digital signal processing, software design, statistical analysis, model fitting, and astrophysics. Funding for the development of the EDGES-2 project is being provided by NSF's Division of Astronomical Sciences through its Advanced Technologies and Instrumentation program.

第一批恒星、星系和黑洞在所谓的“宇宙黎明”期间的形成是观测宇宙学的下一个前沿领域。 在此时期，星系间介质（IGM）主要以中性氢气的形式存在，可以通过其红移的 21 厘米线进行观测。 一旦第一批恒星在红移 z ~ 30 处形成，它们就会产生莱曼-α 光子背景，将中性氢自旋温度与 IGM 中的物理气体温度耦合起来。这被认为是导致 21 厘米线在宇宙微波背景 (CMB) 的吸收中变得可见。 后来，长距离传播的 X 射线将其能量转化为热量，从而提高了 IGM 的温度。这种加热驱动平均 21 cm 信号上升到 CMB 上方的发射，直到中性气体最终在再电离时期被电离，并且没有可检测到的信号残留。早期 IGM 中这些吸收和发射特征的演变在宇宙无线电频谱中应该是明显的，因为红移映射到 21 厘米线的频率。必须解决重大的观测挑战，以将预期的 10-100 mK 高红移 21 cm 信号与主要的银河系前景发射信号分开，但亚利桑那州立大学的 Judd Bowman 博士和他在麻省理工学院的合作者建议克服这些挑战光谱仪的性能提高了 10 倍，频率覆盖范围从 40 到 200 MHz，跨越红移范围 6 z 30，以应对挑战。这种新仪器称为EDGES-2 将利用基于经典噪声波传播模型的推广的新精确校准方法。 该项目的更广泛影响包括演示这种用于宽带系统的新型高精度校准方法，该方法可应用于射电天文学以外的领域，包括电离层研究。该项目还重点为本科生和研究生提供跨学科环境中的培训和指导机会，以学习数字信号处理、软件设计、统计分析、模型拟合和天体物理学的基本原理。 NSF 天文科学部通过其先进技术和仪器计划为 EDGES-2 项目的开发提供资金。