详细研究了ELAIS N1字段与uGMRT -- II。300-500 MHz观测的前景功率谱的源特性和谱变化
Detailed study of ELAIS N1 field with the uGMRT -- II. Source Properties and Spectral Variation Of Foreground Power Spectrum from 300-500 MHz Observations
摘要：
深入了解低频无线电天空对于减去前景是必要的，以便检测来自宇宙黎明，再电离时代（EoR）和后再电离时代的中性氢的红移21厘米信号。在该系列的第二篇论文中，我们提出了在300-500 MHz的ELAIS N1场的升级巨型米波射电望远镜（uGMRT）观测。图像覆盖$\sim 1.8$ $\mathrm{deg}^{2}$区域，中心背景均方根噪声为$\sim$ 15 $μ\mathrm{Jy}$ $\mathrm{beam}^{-1}$。我们提出了一个包含2528个源（流量密度> 100 $μ$ Jy）的射电源目录和归一化源计数。所检测到的源与以前的无线电观测的详细比较。我们讨论了通量尺度的准确性，位置偏移，光谱指数分布和源计数的校正因子。标准化的源计数与以前的观察相同的字段，以及从平方公里阵列设计研究（SKADS）模拟模型源计数。它显示了低于$\sim$ 1 mJy的平坦化，这对应于恒星形成星系和射电宁静AGN人口的增加。本文首次利用射电干涉观测资料估算了银河系同步辐射（DGSE）在$300-500$ ~MHz宽频带上的角功率谱或多频角功率谱（MFAPS）谱特征。这项工作证明了改进的能力的uGMRT。
英文摘要：
Understanding the low-frequency radio sky in depth is necessary to subtract foregrounds in order to detect the redshifted 21 cm signal of neutral hydrogen from the Cosmic Dawn, Epoch of Reionization (EoR) and post-reionization era. In this second paper of the series, we present the upgraded Giant Metrewave Radio Telescope (uGMRT) observation of the ELAIS N1 field made at 300-500 MHz. The image covers an area of $\sim 1.8$ $\mathrm{deg}^{2}$ and has a central background rms noise of $\sim$ 15 $μ\mathrm{Jy}$ $\mathrm{beam}^{-1}$. We present a radio source catalog containing 2528 sources (with flux densities > 100 $μ$Jy) and normalized source counts derived from that. The detailed comparison of detected sources with previous radio observations is shown. We discuss flux scale accuracy, positional offsets, spectral index distribution and correction factors in source counts. The normalized source counts are in agreement with previous observations of the same field, as well as model source counts from the Square Kilometre Array Design Study (SKADS) simulation. It shows a flattening below $\sim$1 mJy which corresponds to rise in population of star forming galaxies and radio-quiet AGN. For the first time, we estimated the spectral characteristics of the angular power spectrum or Multi-Frequency Angular Power Spectrum (MFAPS) of diffuse Galactic synchrotron emission (DGSE) over the wide frequency bandwidth of $300-500$~MHz from radio interferometric observations. This work demonstrates the improved capabilities of the uGMRT.
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