We present the first results of the holographic beam-mapping program for the Canadian Hydrogen Intensity Mapping Experiment (CHIME). We describe the implementation of a holographic technique as adapted for CHIME, and introduce the processing pipeline which prepares the raw holographic timestreams for analysis of beam features. We use data from six bright sources across the full 400–800 MHz observing band of CHIME to provide measurements of the copolar and cross-polar beam response in both amplitude and phase for all 1024 dual-polarized feeds in the array. In addition, we present comparisons with independent probes of the CHIME beam, which indicate the presence of polarized beam leakage. Holographic measurements of the beam have already been applied in science with CHIME, e.g., in estimating the detection significance of far-sidelobe fast radio bursts, and in validating the beam models used for CHIME’s first detections of 21 cm emission (in cross-correlation with measurements of large-scale structure from galaxy surveys and the Lyα forest). Measurements presented in this paper, and future holographic results, will provide a unique data set to characterize the CHIME beam and improve the experiment’s prospects for a detection of the baryon acoustic oscillation signal.

中文翻译：

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加拿大氢强度映射实验 （CHIME） 的全息光束测量


我们展示了加拿大氢强度映射实验 （CHIME） 的全息光束映射程序的初步结果。我们描述了适用于 CHIME 的全息技术的实现，并介绍了为光束特征分析准备原始全息时间流的处理管道。我们使用来自 CHIME 整个 400–800 MHz 观测频带的六个明亮源的数据，为阵列中所有 1024 个双极化馈源的同极和交叉极化光束响应提供幅度和相位的测量。此外，我们还提供了与 CHIME 光束的独立探针的比较，这表明存在偏振光束泄漏。光束的全息测量已经通过 CHIME 应用于科学中，例如，估计远旁瓣快速射电暴的探测意义，以及验证用于 CHIME 首次探测 21 cm 发射的光束模型（与星系巡天和 Lyα 森林的大规模结构测量互相关）。本文中提供的测量结果和未来的全息结果将提供一个独特的数据集来表征 CHIME 光束，并改善实验检测重子声学振荡信号的前景。