论文标题
电离时代21-CM信号观察时期的校准要求 - I.时间相关收益的影响
Calibration Requirements for Epoch of Reionization 21-cm signal observations -- I. Effect of time-correlated gains
论文作者
论文摘要
剩余增益误差增加了无线电干涉测量值的系统。如果进行高动态范围观测，这些系统效应在观察的热噪声上占主导地位。在这项工作中，我们研究了时间相关的残余增益误差在高动态范围观测值中天空亮度分布的功率谱时的效果。特别是，我们讨论了一种方法，以估计在存在明亮的乳层紧凑源的情况下，来自中性氢的红移21 cm信号的功率谱估计器的偏差。我们发现，对于基于可见性的功率谱估计器，尤其是那些使用附近基线相关性来避免噪声偏差，功率谱的偏差主要来自残留增益误差的时间相关性。偏差还取决于特定观察的基线分布。分析计算表明，用于可见性相关性的某些类型的基线对的偏差是主要的。我们在与gmrt阵列（如阵列）存在残留增益误差的情况下对静脉外紧凑源进行了模拟观察，并估计功率谱中的偏差。我们的结果表明，为了估算红移21厘米的功率谱，需要更好的校准技术和估计器开发。
The residual gain errors add to the systematics of the radio interferometric observations. In case of the high dynamic range observations, these systematic effects dominates over the thermal noise of the observation. In this work, we investigate the effect of time-correlated residual gain errors in the estimation of the power spectrum of the sky brightness distribution in high dynamic range observations. Particularly, we discuss a methodology to estimate the bias in the power spectrum estimator of the redshifted 21-cm signal from neutral hydrogen in the presence of bright extragalactic compact sources. We find, that for the visibility based power spectrum estimators, particularly those use nearby baseline correlations to avoid noise bias, the bias in the power spectrum arises mainly from the time correlation in the residual gain error. The bias also depends on the baseline distribution for a particular observation. Analytical calculations show that the bias is dominant for certain types of baseline pairs used for the visibility correlation. We perform simulated observation of extragalactic compact sources in the presence of residual gain errors with the GMRT like array and estimate the bias in the power spectrum. Our results indicate that in order to estimate the redshifted 21-cm power spectrum, better calibration techniques and estimator development are required.
