...界事故 治疗核辐射83天的记录
秦波
摘 要：宇宙再電离观测面临的最大挑战是21 cm信号极为微弱（～10mK）。第一代恒星（6 关键词：数值模拟 射电观测 宇宙再电离 信号处理 Report on “Exploring the Cosmic Reionization Epoch in Frequency Space： An Improved Approach to Remove the Foreground in 21cm Tomography” Qin Bo （National Astronomical Observatories，Chinese Academy of Sciences） Abstract：By adopting a complex foreground model， we re-examine the separation approaches based on the quadratic polynomial fitting technique in frequency spac e in order to investigate whether they work satisfactorily by quantitatively evaluating the quality of restored 21 cm signals （both spectra and power spectra） in terms of sample statistics. We find that a significant part of the Mpc-scale components of the 21 cm signals （75% for & 6 h-1 Mpc scales and 34% for & 1 h-1 Mpc scales） is lost using the traditional separation algorithm， because it tends to be misidentified as part of the foreground when the single-narrow-segment separation approach is applied. The best restoration of the 21 cm signals and the tightest determination of the mean halo b and average ionization fraction xe can be obtained with the three-narrow-segment fitting technique as proposed in this report. Key Words：Numerical simulation； Radio observation； Reionization； Signal processing
