探测宇宙再电离时期的中性氢21厘米辐射

The epoch of reionization (EoR)is an important milestone in the history of the Universe. One of the most promising tool to probe the EoR is the 21 cm hyperfine transition of neutral hydrogen. The signal is sensitive to the emergence of the first luminous objects, radiation from growing massive black holes and the formation of larger groups of galaxies and bright quasars. At the same time it maps the distribution of most of the baryonic matter in the Universe. A number of experiments are set to measure the redshifted 21 cm signal from the EoR. The common denominators of these experiments are the large data sets produced, contaminated by various instrumental effects, ionospheric distortions, RFI and strong Galactic and extragalactic foregrounds. In this research project, we use analytical and numerical approaches to study the experimental challenges involved in detecting the 21 cm signal, with an emphasis on the accurate calibration and foreground removal. These developed techiniques are applied to data from the 21 CentiMeter Array (21CMA) as a demonstration of their value in real-world detections. Experience in the 21CMA pipeline development can offer lessons to the signal-extraction strategy for next-generation low-frequency radio interferometers such as the Square Kilometre Array (SKA).

再电离时期是宇宙历史上一座重要的里程碑，其最有希望的追踪手段之一是中性氢的21厘米超精细跃迁。21厘米信号对第一代发光天体的出现、处于增长期的大质量黑洞的辐射以及较大星系群和明亮类星体群的形成都很灵敏。同时，它还描绘了宇宙中绝大部分重子物质的分布。目前，很多实验都致力于探测来自宇宙再电离时期的21厘米红移信号。这些实验将产生海量的观测数据，并遭受多种观测效应、电离层畸变、射电干扰和强大前景源的污染。在本申请项目中，我们将运用解析和数值的方法研究21厘米实验中面临的观测挑战，重点是精确校准和前景扣除这两个难题。我们计划将发展的数据处理方法运用于21CMA的观测，以此来检验其实用价值。通过完善和发展21CMA的数据处理软件，我们将积累宝贵的21厘米再电离探测的经验，可为下一代低频射电干涉仪（如SKA）的信号提取策略提供借鉴。