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

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

doi:10.1051/0004-6361/202142484

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

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

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Abstract

In this data release from the ongoing LOw-Frequency ARray (LOFAR) Two-metre Sky Survey we present 120a 168 MHz images covering 27% of the northern sky. Our coverage is split into two regions centred at approximately 12h45m +44 30a and 1h00m +28 00a and spanning 4178 and 1457 square degrees respectively. The images were derived from 3451 h (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 6a resolution, our full bandwidth Stokes I continuum maps with a central frequency of 144 MHz have: a median rms sensitivity of 83 μJy beama 1; a flux density scale accuracy of approximately 10%; an astrometric accuracy of 0.2a; and we estimate the point-source completeness to be 90% at a peak brightness of 0.8 mJy beama 1. 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 > a ±a 0.2 which is a consequence of our flux-density scale accuracy and small fractional bandwidth. Our circular polarisation (Stokes V) 20a resolution 120a168 MHz continuum images have a median rms sensitivity of 95 μJy beama 1, 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 480a A a 97.6 kHz wide planes and have a median rms sensitivity per plane of 10.8 mJy beama 1 at 4a and 2.2 mJy beama 1 at 20a; 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.

Original language	English
Article number	A1
Number of pages	27
Journal	Astronomy & Astrophysics
Volume	659
DOIs	https://doi.org/10.1051/0004-6361/202142484
Publication status	Published - 25 Feb 2022

Keywords

astro-ph.GA
astro-ph.CO
astro-ph.HE
astro-ph.IM
Surveys
Techniques: image processing
Radio continuum: general
Catalogs

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10.1051/0004-6361/202142484Licence: Unspecified

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© The European Southern Observatory (ESO).
Accepted author manuscript, 22 MBLicence: CC BY

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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., Weeren, R. J. V., Bester, L., Brüggen, M., Brunetti, G., Callingham, J. R., Chyży, K. T., Conway, J. E., Dijkema, T. J., Duncan, K., ... Zheng, J. (2022). The LOFAR Two-metre Sky Survey -- V. Second data release. Astronomy & Astrophysics, 659, Article A1. https://doi.org/10.1051/0004-6361/202142484

@article{901e3cc9956b4129b4a4a097d46f0373,

title = "The LOFAR Two-metre Sky Survey -- V. Second data release",

abstract = "In this data release from the ongoing LOw-Frequency ARray (LOFAR) Two-metre Sky Survey we present 120a 168 MHz images covering 27% of the northern sky. Our coverage is split into two regions centred at approximately 12h45m +44 30a and 1h00m +28 00a and spanning 4178 and 1457 square degrees respectively. The images were derived from 3451 h (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 6a resolution, our full bandwidth Stokes I continuum maps with a central frequency of 144 MHz have: a median rms sensitivity of 83 μJy beama 1; a flux density scale accuracy of approximately 10%; an astrometric accuracy of 0.2a; and we estimate the point-source completeness to be 90% at a peak brightness of 0.8 mJy beama 1. 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 > a ±a 0.2 which is a consequence of our flux-density scale accuracy and small fractional bandwidth. Our circular polarisation (Stokes V) 20a resolution 120a168 MHz continuum images have a median rms sensitivity of 95 μJy beama 1, 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 480a A a 97.6 kHz wide planes and have a median rms sensitivity per plane of 10.8 mJy beama 1 at 4a and 2.2 mJy beama 1 at 20a; 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.",

keywords = "astro-ph.GA, astro-ph.CO, astro-ph.HE, astro-ph.IM, Surveys, Techniques: image processing, Radio continuum: general, Catalogs",

author = "Shimwell, {T. W.} and Hardcastle, {M. J.} and C. Tasse and Best, {P. N.} and R{\"o}ttgering, {H. J. A.} and Williams, {W. L.} and A. Botteon and A. Drabent and A. Mechev and A. Shulevski and Weeren, {R. J. van} and L. Bester and M. Br{\"u}ggen and G. Brunetti and Callingham, {J. R.} and Chy{\.z}y, {K. T.} and Conway, {J. E.} and Dijkema, {T. J.} and K. Duncan and Gasperin, {F. de} and Hale, {C. L.} and M. Haverkorn and B. Hugo and N. Jackson and M. Mevius and Miley, {G. K.} and Morabito, {L. K.} and R. Morganti and A. Offringa and Oonk, {J. B. R.} and D. Rafferty and J. Sabater and Smith, {D. J. B.} and Schwarz, {D. J.} and O. Smirnov and O'Sullivan, {S. P.} and H. Vedantham and White, {G. J.} and Albert, {J. G.} and L. Alegre and B. Asabere and Bacon, {D. J.} and A. Bonafede and E. Bonnassieux and M. Brienza and M. Bilicki and M. Bonato and Rivera, {G. Calistro} and R. Cassano and R. Cochrane and Croston, {J. H.} and V. Cuciti and D. Dallacasa and A. Danezi and Dettmar, {R. J.} and Gennaro, {G. Di} and Edler, {H. W.} and En{\ss}lin, {T. A.} and Emig, {K. L.} and Franzen, {T. M. O.} and C. Garc{\'i}a-Vergara and Grange, {Y. G.} and G. G{\"u}rkan and M. Hajduk and G. Heald and V. Heesen and Hoang, {D. N.} and M. Hoeft and C. Horellou and M. Iacobelli and M. Jamrozy and V. Jeli{\'c} and R. Kondapally and P. Kukreti and M. Kunert-Bajraszewska and M. Magliocchetti and V. Mahatma and K. Ma{\l}ek and S. Mandal and F. Massaro and Z. Meyer-Zhao and B. Mingo and Mostert, {R. I. J.} and Nair, {D. G.} and Nakoneczny, {S. J.} and B. Nikiel-Wroczy{\'n}ski and E. Orr{\'u} and U. Pajdosz-{\'S}mierciak and T. Pasini and I. Prandoni and Piggelen, {H. E. van} and K. Rajpurohit and E. Retana-Montenegro and Riseley, {C. J.} and A. Rowlinson and A. Saxena and C. Schrijvers and F. Sweijen and Siewert, {T. M.} and R. Timmerman and M. Vaccari and J. Vink and West, {J. L.} and A. Wo{\l}owska and X. Zhang and J. Zheng",

note = "{\textcopyright} The European Southern Observatory (ESO). ",

year = "2022",

month = feb,

day = "25",

doi = "10.1051/0004-6361/202142484",

language = "English",

volume = "659",

journal = "Astronomy & Astrophysics",

issn = "0004-6361",

publisher = "EDP Sciences",

}

Shimwell, TW, Hardcastle, MJ, Tasse, C, Best, PN, Röttgering, HJA, Williams, WL, Botteon, A, Drabent, A, Mechev, A, Shulevski, A, Weeren, RJV, Bester, L, Brüggen, M, Brunetti, G, Callingham, JR, Chyży, KT, Conway, JE, Dijkema, TJ, Duncan, K, Gasperin, FD, Hale, CL, Haverkorn, M, Hugo, B, Jackson, N, Mevius, M, Miley, GK, Morabito, LK, Morganti, R, Offringa, A, Oonk, JBR, Rafferty, D, Sabater, J, Smith, DJB, Schwarz, DJ, Smirnov, O, O'Sullivan, SP, Vedantham, H, White, GJ, Albert, JG, Alegre, L, Asabere, B, Bacon, DJ, Bonafede, A, Bonnassieux, E, Brienza, M, Bilicki, M, Bonato, M, Rivera, GC, Cassano, R, Cochrane, R, Croston, JH, Cuciti, V, Dallacasa, D, Danezi, A, Dettmar, RJ, Gennaro, GD, Edler, HW, Enßlin, TA, Emig, KL, Franzen, TMO, García-Vergara, C, Grange, YG, Gürkan, G, Hajduk, M, Heald, G, Heesen, V, Hoang, DN, 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, RIJ, Nair, DG, Nakoneczny, SJ, Nikiel-Wroczyński, B, Orrú, E, Pajdosz-Śmierciak, U, Pasini, T, Prandoni, I, Piggelen, HEV, Rajpurohit, K, Retana-Montenegro, E, Riseley, CJ, Rowlinson, A, Saxena, A, Schrijvers, C, Sweijen, F, Siewert, TM, Timmerman, R, Vaccari, M, Vink, J, West, JL, Wołowska, A, Zhang, X & Zheng, J 2022, 'The LOFAR Two-metre Sky Survey -- V. Second data release', Astronomy & Astrophysics, vol. 659, A1. https://doi.org/10.1051/0004-6361/202142484

TY - JOUR

T1 - The LOFAR Two-metre Sky Survey -- V. Second data release

AU - Shimwell, T. W.

AU - Hardcastle, M. J.

AU - Tasse, C.

AU - Best, P. N.

AU - Röttgering, H. J. A.

AU - Williams, W. L.

AU - Botteon, A.

AU - Drabent, A.

AU - Mechev, A.

AU - Shulevski, A.

AU - Weeren, R. J. van

AU - Bester, L.

AU - Brüggen, M.

AU - Brunetti, G.

AU - Callingham, J. R.

AU - Chyży, K. T.

AU - Conway, J. E.

AU - Dijkema, T. J.

AU - Duncan, K.

AU - Gasperin, F. de

AU - Hale, C. L.

AU - Haverkorn, M.

AU - Hugo, B.

AU - Jackson, N.

AU - Mevius, M.

AU - Miley, G. K.

AU - Morabito, L. K.

AU - Morganti, R.

AU - Offringa, A.

AU - Oonk, J. B. R.

AU - Rafferty, D.

AU - Sabater, J.

AU - Smith, D. J. B.

AU - Schwarz, D. J.

AU - Smirnov, O.

AU - O'Sullivan, S. P.

AU - Vedantham, H.

AU - White, G. J.

AU - Albert, J. G.

AU - Alegre, L.

AU - Asabere, B.

AU - Bacon, D. J.

AU - Bonafede, A.

AU - Bonnassieux, E.

AU - Brienza, M.

AU - Bilicki, M.

AU - Bonato, M.

AU - Rivera, G. Calistro

AU - Cassano, R.

AU - Cochrane, R.

AU - Croston, J. H.

AU - Cuciti, V.

AU - Dallacasa, D.

AU - Danezi, A.

AU - Dettmar, R. J.

AU - Gennaro, G. Di

AU - Edler, H. W.

AU - Enßlin, T. A.

AU - Emig, K. L.

AU - Franzen, T. M. O.

AU - García-Vergara, C.

AU - Grange, Y. G.

AU - Gürkan, G.

AU - Hajduk, M.

AU - Heald, G.

AU - Heesen, V.

AU - Hoang, D. N.

AU - Hoeft, M.

AU - Horellou, C.

AU - Iacobelli, M.

AU - Jamrozy, M.

AU - Jelić, V.

AU - Kondapally, R.

AU - Kukreti, P.

AU - Kunert-Bajraszewska, M.

AU - Magliocchetti, M.

AU - Mahatma, V.

AU - Małek, K.

AU - Mandal, S.

AU - Massaro, F.

AU - Meyer-Zhao, Z.

AU - Mingo, B.

AU - Mostert, R. I. J.

AU - Nair, D. G.

AU - Nakoneczny, S. J.

AU - Nikiel-Wroczyński, B.

AU - Orrú, E.

AU - Pajdosz-Śmierciak, U.

AU - Pasini, T.

AU - Prandoni, I.

AU - Piggelen, H. E. van

AU - Rajpurohit, K.

AU - Retana-Montenegro, E.

AU - Riseley, C. J.

AU - Rowlinson, A.

AU - Saxena, A.

AU - Schrijvers, C.

AU - Sweijen, F.

AU - Siewert, T. M.

AU - Timmerman, R.

AU - Vaccari, M.

AU - Vink, J.

AU - West, J. L.

AU - Wołowska, A.

AU - Zhang, X.

AU - Zheng, J.

PY - 2022/2/25

Y1 - 2022/2/25

N2 - In this data release from the ongoing LOw-Frequency ARray (LOFAR) Two-metre Sky Survey we present 120a 168 MHz images covering 27% of the northern sky. Our coverage is split into two regions centred at approximately 12h45m +44 30a and 1h00m +28 00a and spanning 4178 and 1457 square degrees respectively. The images were derived from 3451 h (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 6a resolution, our full bandwidth Stokes I continuum maps with a central frequency of 144 MHz have: a median rms sensitivity of 83 μJy beama 1; a flux density scale accuracy of approximately 10%; an astrometric accuracy of 0.2a; and we estimate the point-source completeness to be 90% at a peak brightness of 0.8 mJy beama 1. 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 > a ±a 0.2 which is a consequence of our flux-density scale accuracy and small fractional bandwidth. Our circular polarisation (Stokes V) 20a resolution 120a168 MHz continuum images have a median rms sensitivity of 95 μJy beama 1, 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 480a A a 97.6 kHz wide planes and have a median rms sensitivity per plane of 10.8 mJy beama 1 at 4a and 2.2 mJy beama 1 at 20a; 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.

AB - In this data release from the ongoing LOw-Frequency ARray (LOFAR) Two-metre Sky Survey we present 120a 168 MHz images covering 27% of the northern sky. Our coverage is split into two regions centred at approximately 12h45m +44 30a and 1h00m +28 00a and spanning 4178 and 1457 square degrees respectively. The images were derived from 3451 h (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 6a resolution, our full bandwidth Stokes I continuum maps with a central frequency of 144 MHz have: a median rms sensitivity of 83 μJy beama 1; a flux density scale accuracy of approximately 10%; an astrometric accuracy of 0.2a; and we estimate the point-source completeness to be 90% at a peak brightness of 0.8 mJy beama 1. 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 > a ±a 0.2 which is a consequence of our flux-density scale accuracy and small fractional bandwidth. Our circular polarisation (Stokes V) 20a resolution 120a168 MHz continuum images have a median rms sensitivity of 95 μJy beama 1, 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 480a A a 97.6 kHz wide planes and have a median rms sensitivity per plane of 10.8 mJy beama 1 at 4a and 2.2 mJy beama 1 at 20a; 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.

KW - astro-ph.GA

KW - astro-ph.CO

KW - astro-ph.HE

KW - astro-ph.IM

KW - Surveys

KW - Techniques: image processing

KW - Radio continuum: general

KW - Catalogs

UR - http://www.scopus.com/inward/record.url?scp=85124078800&partnerID=8YFLogxK

U2 - 10.1051/0004-6361/202142484

DO - 10.1051/0004-6361/202142484

M3 - Article

SN - 0004-6361

VL - 659

JO - Astronomy & Astrophysics

JF - Astronomy & Astrophysics

M1 - A1

ER -

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

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