Lofar两米的天空调查-V。第二个数据发布

论文标题

Lofar两米的天空调查-V。第二个数据发布

The LOFAR Two-metre Sky Survey -- V. Second data release

论文作者

Shimwell, T. W., Hardcastle, M. J., Tasse, C., Best, P. N., Röttgering, H. J. A., Williams, W. L., Botteon, A., Drabent, A., Mechev, A., Shulevski, A., van Weeren, R. J., Bester, L., Brüggen, M., Brunetti, G., Callingham, J. R., Chyży, K. T., Conway, J. E., Dijkema, T. J., Duncan, K., de Gasperin, F., Hale, C. L., Haverkorn, M., Hugo, B., Jackson, N., Mevius, M., Miley, G. K., Morabito, L. K., Morganti, R., Offringa, A., Oonk, J. B. R., Rafferty, D., Sabater, J., Smith, D. J. B., Schwarz, D. J., Smirnov, O., O'Sullivan, S. P., Vedantham, H., White, G. J., Albert, J. G., Alegre, L., Asabere, B., Bacon, D. J., Bonafede, A., Bonnassieux, E., Brienza, M., Bilicki, M., Bonato, M., Rivera, G. Calistro, Cassano, R., Cochrane, R., Croston, J. H., Cuciti, V., Dallacasa, D., Danezi, A., Dettmar, R. J., Di Gennaro, G., Edler, H. W., Enßlin, T. A., Emig, K. L., Franzen, T. M. O., García-Vergara, C., Grange, Y. G., Gürkan, G., Hajduk, M., Heald, G., Heesen, V., Hoang, D. N., Hoeft, M., Horellou, C., Iacobelli, M., Jamrozy, M., Jelić, V., Kondapally, R., Kukreti, P., Kunert-Bajraszewska, M., Magliocchetti, M., Mahatma, V., Małek, K., Mandal, S., Massaro, F., Meyer-Zhao, Z., Mingo, B., Mostert, R. I. J., Nair, D. G., Nakoneczny, S. J., Nikiel-Wroczyński, B., Orrú, E., Pajdosz-Śmierciak, U., Pasini, T., Prandoni, I., van Piggelen, H. E., Rajpurohit, K., Retana-Montenegro, E., Riseley, C. J., Rowlinson, A., Saxena, A., Schrijvers, C., Sweijen, F., Siewert, T. M., Timmerman, R., Vaccari, M., Vink, J., West, J. L., Wołowska, A., Zhang, X., Zheng, J.

论文摘要

在此数据发布中，我们提出了120-168MHz图像，覆盖了北方天空的27％。我们的覆盖范围分为两个区域，居中约为12h45m +44 $^\ circ $ 30'和1h 00m +28 $^\ circ $ 00'，分别跨越4178和1457平方度。这些图像源自Lofar高带天线数据的3,451小时（7.6 pb），这些数据在广泛但完全自动化的数据处理过程中对方向无关的仪器特性以及方向依赖性的离子层变形进行了校正。 4,396,228个无线电来源的目录源自我们的总强度（Stokes I）地图，其中大多数以前从未在无线电波长上检测到其中大多数。在6英寸的分辨率下，我们的完整带宽stokes I连续映射的中心频率为144MHz：中间RMS灵敏度为83 $μ$ jy/beam/beam/beam;通量密度尺度的精度约为10％； Astromentric精度为0.2”；我们估计，在0.8MJY/BEAM的峰值亮度下，点源的完整性为90％。通过在整个频段上创建三个16MHz带宽图像，我们能够测量许多来源的频段频谱指数，尽管在+/- 0.2的派生频谱指数上有误差，这是我们磁通量密度尺度精度和小的分数带宽的结果。 Our circular polarisation (Stokes V) 20" resolution 120-168MHz continuum images have a median rms sensitivity of 95$μ$Jy/beam, and we estimate a Stokes I to Stokes V leakage of 0.056%. Our linear polarisation (Stokes Q and Stokes U) image cubes consist of 480 x 97.6 kHz wide planes and have a median rms sensitivity per plane在4'时为10.8mjy/beam，在20英寸时；我们估计stokes I将Q/U泄漏量约为0.2％。在这里，我们表征并公开发布了我们的Stokes I，Q，U和V图像，除了校准的UV-DATA之外。

In this data release from the LOFAR Two-metre Sky Survey (LoTSS) we present 120-168MHz images covering 27% of the northern sky. Our coverage is split into two regions centred at approximately 12h45m +44$^\circ$30' and 1h00m +28$^\circ$00' and spanning 4178 and 1457 square degrees respectively. The images were derived from 3,451hrs (7.6PB) of LOFAR High Band Antenna data which were corrected for the direction-independent instrumental properties as well as direction-dependent ionospheric distortions during extensive, but fully automated, data processing. A catalogue of 4,396,228 radio sources is derived from our total intensity (Stokes I) maps, where the majority of these have never been detected at radio wavelengths before. At 6" resolution, our full bandwidth Stokes I continuum maps with a central frequency of 144MHz have: a median rms sensitivity of 83$μ$Jy/beam; a flux density scale accuracy of approximately 10%; an astrometric accuracy of 0.2"; and we estimate the point-source completeness to be 90% at a peak brightness of 0.8mJy/beam. By creating three 16MHz bandwidth images across the band we are able to measure the in-band spectral index of many sources, albeit with an error on the derived spectral index of +/-0.2 which is a consequence of our flux-density scale accuracy and small fractional bandwidth. Our circular polarisation (Stokes V) 20" resolution 120-168MHz continuum images have a median rms sensitivity of 95$μ$Jy/beam, and we estimate a Stokes I to Stokes V leakage of 0.056%. Our linear polarisation (Stokes Q and Stokes U) image cubes consist of 480 x 97.6 kHz wide planes and have a median rms sensitivity per plane of 10.8mJy/beam at 4' and 2.2mJy/beam at 20"; we estimate the Stokes I to Stokes Q/U leakage to be approximately 0.2%. Here we characterise and publicly release our Stokes I, Q, U and V images in addition to the calibrated uv-data.

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