One- and two-point source statistics from the LOFAR Two-metre Sky Survey first data release
One- and two-point source statistics from the LOFAR Two-metre Sky Survey first data release
复制标题
LOFAR 两米巡天首次数据发布的单点和两点源统计数据
DOI：
10.1051/0004-6361/201936592
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发表时间：
2019
影响因子：
6.5
通讯作者：
W. Williams
中科院分区：
文献类型：
--
作者：
T. M. Siewert;C. Hale;N. Bhardwaj;Marian Biermann;D. Bacon;M. Jarvis;H. Rottgering;D. Schwarz;T. Shimwell;P. Best;K. Duncan;M. Hardcastle;J. Sabater;C. Tasse;G. White;W. Williams
LOFAR两米巡天(LOTSS)最终将绘制完整的北方天空图，并为研究宇宙大尺度结构的分布和演化提供一个很好的机会。目的：通过将LOTSS首次数据发布(DR1)星表与建立的统计各向同性和均匀宇宙的宇宙学模型的期望进行统计比较，检验LOTSS观测的质量。方法研究点源完备性并定义几种质量切割，以确定单元内计数统计量和差分源计数统计量，并测量角两点关联函数。我们使用大约一半的LoTSS-DR1射电源的光度红移估计来比较宇宙历史上的星团。结果对于掩蔽的LoTSS-DR1增值源星表，我们发现在0.8mJy的通量密度之上，点源完备度为99%。单元计数统计表明，射电源的分布不能用空间泊松过程来描述。相反，复合泊松分布提供了一个很好的拟合。差异源计数与以前在低射电频率的深场中的发现以及SKA设计研究和分层射电河外连续谱模拟的模拟星表很好地一致。将附加源目录限制在低噪声区域，并应用2mJy的通量密度阈值，可以提供我们对角两点关联的最可靠估计。基于光度红移分布和Planck2018最佳拟合宇宙学模型，理论预测的0.1°到6°之间的角两点关联与具有红移信息的射电源子样本的测量聚集性很好地吻合。结论偏离泊松分布可能是由于大量分辨射电源的多分量性质和/或通量密度校准的不确定性的结果。角两点相关函数为<；10−，角尺度为>；1°，最大为所探测的最大尺度。在磁通密度阈值为2mJy，枢轴角度为1°时，我们得到了 = (5.1 ± 0.6)×10−3的团簇振幅，斜率参数为γ = 0.74 ± 0.16。对于较小的通量密度阈值，确定了系统性问题，这很可能与单个点的通量密度校准有关。我们的结论是，我们发现与射电天空在百分比水平上的大尺度统计各向同性的预期是一致的。角两点关联很好地符合宇宙标准模型的预期。
Context.The LOFAR Two-metre Sky Survey (LoTSS) will eventually map the complete Northern sky and provide an excellent opportunity to study the distribution and evolution of the large-scale structure of the Universe.Aims.We test the quality of LoTSS observations through a statistical comparison of the LoTSS first data release (DR1) catalogues to expectations from the established cosmological model of a statistically isotropic and homogeneous Universe.Methods.We study the point-source completeness and define several quality cuts, in order to determine the count-in-cell statistics and differential source count statistics, and measure the angular two-point correlation function. We use the photometric redshift estimates, which are available for about half of the LoTSS-DR1 radio sources, to compare the clustering throughout the history of the Universe.Results.For the masked LoTSS-DR1 value-added source catalogue, we find a point-source completeness of 99% above flux densities of 0.8 mJy. The counts-in-cell statistic reveals that the distribution of radio sources cannot be described by a spatial Poisson process. Instead, a good fit is provided by a compound Poisson distribution. The differential source counts are in good agreement with previous findings in deep fields at low radio frequencies and with simulated catalogues from the SKA Design Study and the Tiered Radio Extragalactic Continuum Simulation. Restricting the value added source catalogue to low-noise regions and applying a flux density threshold of 2 mJy provides our most reliable estimate of the angular two-point correlation. Based on the distribution of photometric redshifts and thePlanck2018 best-fit cosmological model, the theoretically predicted angular two-point correlation between 0.1 deg and 6 deg agrees reasonably well with the measured clustering for the sub-sample of radio sources with redshift information.Conclusions.The deviation from a Poissonian distribution might be a consequence of the multi-component nature of a large number of resolved radio sources and/or of uncertainties on the flux density calibration. The angular two-point correlation function is < 10−2at angular scales > 1 deg and up to the largest scales probed. At a 2 mJy flux density threshold and at a pivot angle of 1 deg, we find a clustering amplitude ofA = (5.1 ± 0.6) × 10−3with a slope parameter ofγ = 0.74 ± 0.16. For smaller flux density thresholds, systematic issues are identified, which are most likely related to the flux density calibration of the individual pointings. We conclude that we find agreement with the expectation of large-scale statistical isotropy of the radio sky at the per cent level. The angular two-point correlation agrees well with the expectation of the cosmological standard model.
影响因子：
6.5
作者：
T. Shimwell;H. Röttgering;P. Best;W. Williams;T. J. Dijkema;F. Gasperin;M. Hardcastle;G. Heald
通讯作者：
T. Shimwell;H. Röttgering;P. Best;W. Williams;T. J. Dijkema;F. Gasperin;M. Hardcastle;G. Heald
影响因子：
6.5
作者：
van Haarlem, M. P.;Wise, M. W.;van Zwieten, J.
通讯作者：
van Zwieten, J.