标题： 高红移21厘米观测中漫射银河系辐射对方向无关增益校准的影响 显示英文标题

标题： The impact of diffuse Galactic emission on direction-independent gain calibration in high-redshift 21 cm observations

摘要： 这项研究检查了弥散银河系辐射对基于天空的独立方向（DI）增益校准的影响，使用了低频阵列（LOFAR）在再电离时期（EoR）对高红移中性氢21厘米信号进行的真实正向模拟观测。 我们使用包含点源目录和弥散银河系辐射的天空模型，模拟了LOFAR在147 - 159 MHz之间的观测。 模拟观测仅使用点源目录进行了DI增益校准，利用了LOFAR-EoR数据分析流程。 进行了完整的功率谱分析，以评估使用完整和不完整天空模型进行DI增益校准引入的系统偏差，相对于热噪声。 此外，计算了观测对之间的交叉相干性，以确定DI增益校准误差在功率谱空间特定区域是否随积分时间而具有相干性或非相干性。 我们发现，使用省略弥散银河系辐射的不完整天空模型进行DI增益校准会在$k_{\parallel}$个bin < 0.2 $h\,\mathrm{Mpc}^{-1}$中引入功率谱的系统偏差。 这些bin中的功率谱误差是相干的；因此，可以在前景去除步骤中减轻由此产生的偏差。 相反，对于$k_{\parallel}$> 0.2 $h\,\mathrm{Mpc}^{-1}$的误差主要是非相干的，并随着噪声平均下来。 我们得出结论，天空模型中缺少弥散银河系辐射不是当前LOFAR-EoR对21厘米信号功率谱上限结果中观察到的过量噪声的主要贡献因素。 显示英文摘要

摘要： This study examines the impact of diffuse Galactic emission on sky-based direction-independent (DI) gain calibration using realistic forward simulations of Low-Frequency Array (LOFAR) observations of the high-redshift 21 cm signal of neutral hydrogen during the Epoch of Reionization (EoR). We simulated LOFAR observations between 147 - 159 MHz using a sky model that includes a point source catalogue and diffuse Galactic emission. The simulated observations were DI-gain calibrated with the point source catalogue alone, utilising the LOFAR-EoR data analysis pipeline. A full power spectrum analysis was conducted to assess the systematic bias introduced by DI-gain calibration using complete and incomplete sky models, relative to thermal noise. Additionally, the cross-coherence between observation pairs was computed to determine whether DI-gain calibration errors are coherent or incoherent in specific regions of power spectrum space as a function of integration time. We find that DI-gain calibration with an incomplete sky model that omits diffuse Galactic emission introduces a systematic bias in the power spectrum for $k_{\parallel}$ bins < 0.2 $h\,\mathrm{Mpc}^{-1}$. The power spectrum errors in these bins are coherent; therefore, the resulting bias can be mitigated during the foreground removal step. In contrast, errors for $k_{\parallel}$ > 0.2 $h\,\mathrm{Mpc}^{-1}$ are largely incoherent and average down as noise. We conclude that missing diffuse Galactic emission in the sky model is not a significant contributor to the excess noise observed in the current LOFAR-EoR upper limit results on the 21 cm signal power spectrum.