Published January 1, 2022 | Version v1
Dataset Open

The LOFAR Two-metre Sky Survey (LoTSS) V. Second data release (P012+36)

Description

In this data release from the ongoing LOw-Frequency ARray (LOFAR) Two-metre Sky Survey (LoTSS) we present 120-168 MHz images covering 27% of the northern sky. Our coverage is split into two regions centred at approximately 12h45m +44◦30′ and 1h00m +28◦ 00′ and spanning 4178 and 1457 square degrees respectively. The images were derived from 3,451 hrs (7.6 PB) 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 144 MHz 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 0.8 mJy/beam. By creating three 16 MHz 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 120-168 MHz 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 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 to facilitate the thorough scientific exploitation of this unique dataset.

This is field P012+36.

Files

Files (198.7 GB)

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fits_headers.tar

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images.tar

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low-mosaic-blanked.fits

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low-mosaic-weights.fits

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misc.tar

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mosaic-blanked.fits

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mosaic-blanked.png

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mosaic-weights.fits

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mosaic.pybdsmmask.fits

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mosaic.resid.fits

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mosaic.rms.fits

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rmsynth.tar

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stokes_large.tar

36.8 GB
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stokes_small.tar

866.6 MB
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uv.tar

134.9 GB
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Additional details

Dates

Created
2021-11-25
Updated
2022-08-16

Collection

Metadata
$schema https://repository.surf.nl/schema/lotss-dr2
accref https://sdc-dev.astron.nl/vodev/getproduct/LoTSS-DR2/P012%2B36
centeralpha 12.9424
centerdelta 36.0576
instid LOFAR.HBA
dateobs 57664.8131365739
naxes 2
pixelsize 8926, 8926
pixelscale 0.0004166669968981296, 0.0004166669968981296
refframe ICRS
wcs_equinox 2000.0
wcs_projection SIN
wcs_refpixel 4463.0, 4463.0
wcs_refvalues 12.9424, 36.0576
wcs_cdmatrix -0.0004166669968981296, 0.0, 0.0, 0.0004166669968981296
bandpassid 120-168MHz
bandpassunit m
bandpassrefval 2.08189
bandpasshi 2.49827
bandpasslo 1.78448
pixflags Z
coverage 15.190220190627583, 34.176626967942205, 15.299011217499466, 37.894990401135544, 10.58526065651229, 37.89498030495445, 10.694076037743875, 34.17661733760032
mosaic_id P012+36
related_products https://sdc-dev.astron.nl/vodev/lotss_dr2/q/dlmosaic/dlmeta?ID=ivo%3A//ASTRONSDCv/%7E%3FLoTSS-DR2/P012%2B36

Contact

Contact Email
shimwell@astron.nl