The detection of redshifted hyperfine line of neutral hydrogen (H i) is the most promising probe of the epoch of reionization (EoR). We report an analysis of 55 h of Murchison Widefield Array (MWA) phase II drift scan EoR data. The data correspond to a central frequency $\nu _0 = 154.24 \, \rm MHz$ (z ≃ 8.2 for the redshifted H i hyperfine line) and bandwidth $B = 10.24 \, \rm MHz$. As one expects greater system stability in a drift scan, we test the system stability by comparing the extracted power spectra from data with noise simulations and show that the power spectra for the cleanest data behave as thermal noise. We compute the H i power spectrum as a function of time in one and two dimensions. The best upper limit on the 1D power spectrum are: $\Delta ^2(k) \simeq (1000~\rm mK)^2$ at k ≃ 0.2h Mpc−1 and at k ≃ 1h Mpc−1. The cleanest modes, which might be the most suited for obtaining the optimal signal to noise, correspond to k ≳ 1h Mpc−1. We also study the time-dependence of the foreground-dominated modes in a drift scan and compare with the expected behaviour.

中文翻译：

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使用 MWA 漂移扫描数据提取 21 cm EoR 信号

中性氢（H i）红移超细线的探测是再电离时代（EoR）最有希望的探测。我们报告了对默奇森宽场阵列 (MWA) 阶段 II 漂移扫描 EoR 数据的 55 小时分析。数据对应于中心频率 $\nu_0 = 154.24 \, \rm MHz$（对于红移的 H i 超细线，z ≃ 8.2）和带宽 $B = 10.24 \, \rm MHz$。由于人们期望在漂移扫描中具有更高的系统稳定性，我们通过比较从数据中提取的功率谱与噪声模拟来测试系统稳定性，并表明最干净数据的功率谱表现为热噪声。我们将 H i 功率谱计算为一维和二维时间的函数。一维功率谱的最佳上限是：$\Delta ^2(k) \simeq (1000~\rm mK)^2$ at k ≃ 0.2h Mpc−1 和 at k ≃ 1h Mpc−1。最干净的模式，这可能最适合获得最佳信噪比，对应于 k ≳ 1h Mpc-1。我们还研究了漂移扫描中前景主导模式的时间依赖性，并与预期行为进行了比较。