论文标题
Lofar两米的天空调查：深场。 ii。 Elais-n1 Lofar Deep Field
The LOFAR Two Metre Sky Survey: Deep Fields. II. The ELAIS-N1 LOFAR deep field
论文作者
论文摘要
Lofar两米的天空调查（批次）将覆盖北部的整个天空，此外，旨在在具有最广泛的辅助数据的区域内观察到噪声水平〜10 microjy/bm的噪声水平〜10 microjy/bm。本文介绍了Elais-N1 Deep Field，这是迄今为止最深层的深层领域。在有效观察时间为163.7小时的情况下，它在中央区域（超过10平方度的Microjy/bm以下）达到低于20 microjy/bm的根平方（RMS）噪声水平。该分辨率为6个ARCSEC，在整个区域（68平方摄氏度）中检测到84862个无线电来源，最高质量区域的74127源距离指向中心小于3度。该观测值达到的天空密度为每平方英尺5000多个来源。在中央〜5平方米。地区。我们介绍了校准过程，该过程解决了一些观测值的特殊配置以及与标准批次相比，涵盖的扩展带宽（115至177 MHz；中央频率146.2 MHz）。我们还描述了使用文献中其他无线电调查检测到的来源进行交叉匹配来校准通量密度量表的方法。我们发现与通量密度量表有关的通量密度不确定性约为6.5％。通过研究不同时期之间的通量密度测量的变化，我们表明相对通量密度校准可靠地可靠地半径约3度，但是所有来源的额外通量密度不确定性都在大约3％的水平上存在。这可能与残留校准误差有关，并且显示在离电层条件较差的数据集中更为重要。我们还提供带内光谱指数，这对于检测具有异常光谱特性的来源很有用。 Elais-N1的通量密度的最终不确定性估计为约10％。
The LOFAR Two-metre Sky Survey (LoTSS) will cover the full northern sky and, additionally, aims to observe the LoTSS deep fields to a noise level of ~10 microJy/bm over several tens of square degrees in areas that have the most extensive ancillary data. This paper presents the ELAIS-N1 deep field, the deepest of the LoTSS deep fields to date. With an effective observing time of 163.7 hours, it reaches a root mean square (RMS) noise level below 20 microJy/bm in the central region (and below 30 microJy/bm over 10 square degrees). The resolution is 6 arcsecs and 84862 radio sources were detected in the full area (68 sq. deg.) with 74127 sources in the highest quality area at less than 3 degrees from the pointing centre. The observation reaches a sky density of more than 5000 sources per sq. deg. in the central ~5 sq. deg. region. We present the calibration procedure, which addresses the special configuration of some observations and the extended bandwidth covered (115 to 177 MHz; central frequency 146.2 MHz) compared to standard LoTSS. We also describe the methods used to calibrate the flux density scale using cross-matching with sources detected by other radio surveys in the literature. We find the flux density uncertainty related to the flux density scale to be ~6.5%. By studying the variations of the flux density measurements between different epochs, we show that relative flux density calibration is reliable out to about a 3 degree radius, but that additional flux density uncertainty is present for all sources at about the 3 per cent level; this is likely to be associated with residual calibration errors, and is shown to be more significant in datasets with poorer ionosphere conditions. We also provide intra-band spectral indices, which can be useful to detect sources with unusual spectral properties. The final uncertainty in the flux densities is estimated to be ~10% for ELAIS-N1.
