发表机构
University of Cambridge; Cavendish Laboratory, University of Cambridge; Kavli Institute for Cosmology in Cambridge, University of Cambridge（剑桥大学; 剑桥大学卡文迪许实验室; 剑桥大学卡弗里宇宙学研究所）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究量化了全球21厘米实验波束色差校正所需的天图分辨率，发现约1°的分辨率降级不会引入可测量的残差增幅，为相关实验的天区模型设计提供了实用约束。
AI 中文摘要
中性氢的21厘米超精细跃迁是少数能直接探测早期宇宙历史的探针之一。该信号的高红移探测可揭示目前人类对宇宙史中最不了解的黑暗时代和宇宙黎明时期的认知。然而，该信号被明亮的前景辐射所掩盖，且会因探测天线的色差发生畸变。校正色差需要在相关频率范围内准确表征射电天图。但用于该校正的基础天图，如全球天图模型（Global Sky Model, GSM）的实例，受限于分辨率、校准和外推不确定性，尤其在缩放到与宇宙黎明研究相关的较低频率时问题更突出。本研究量化了基础天图需以何种精度表征真实天区，才能生成可靠的波束校正。利用模拟天区数据，我们从逐步降分辨率的基础天图生成波束色差校正，并将其与基于全分辨率天图的校正效果进行对比。我们发现，当天图分辨率降至约1°时，在进行色差校正并扣除三种不同前景模型（两个多项式和一个幂律展开）时，残差幅度未出现可测量的增加。这些结果为波束校正流程中使用的天区模型所需的分辨率和精度提供了实用约束，为未来全球21厘米实验的设计与校准策略，以及低频天图绘制工作提供了参考。
英文摘要
The 21 cm hyperfine transition of neutral hydrogen provides one of the few direct probes of the early cosmic history. High-redshift detections of this signal could shine light on the poorly understood epochs of the Dark Ages and Cosmic Dawn, periods that remain among the least understood in the Universe's history. However, this signal is masked by bright foregrounds and is distorted by the chromaticity of the antenna used to detect it. Correcting for the chromaticity requires an accurate representation of the radio sky across relevant frequencies. However, base sky maps used for this correction, such as instances of the Global Sky Model (GSM), are limited by resolution, calibration and extrapolation uncertainties, especially when scaled to lower frequencies relevant for Cosmic Dawn studies. This work quantifies how accurately the base map must represent the true sky to produce a reliable beam correction. Using simulated sky data, we generate beam chromaticity corrections generated from progressively degraded versions of the base map, and compare how well they do in comparison to a correction based on the full-resolution map. We find that degradation in map resolution of $\sim 1^\circ$ does not introduce measurable increases in the amplitude of the residuals when correcting for the chromaticity and subtracting three different foreground models (two polynomials and a power law expansion). These results provide practical constraints on the required resolution and accuracy of sky models used in beam correction pipelines, informing future design and calibration strategies for global 21 cm experiments, and future efforts to map the low frequency sky.
