J/A+A/648/A104 LOFAR LBA Sky Survey. I. (de Gasperin+, 2021)
The LOFAR LBA Sky Survey. I. Survey description and preliminary data release.
de Gasperin F., Williams W.L., Best P., Brueggen M., Brunetti G.,
Cuciti V., Dijkema T.J., Hardcastle M.J., Norden M.J., Offringa A.,
Shimwell T., van Weeren R., Bomans D., Bonafede A., Botteon A.,
Callingham J.R., Cassano R., Chyzy K.T., Emig K.L., Edler H., Haverkorn M.,
Heald G., Heesen V., Iacobelli M., Intema H.T., Kadler M., Malek K.,
Mevius M., Miley G., Mingo B., Morabito L.K., Sabater J., Morganti R.,
Orru E., Pizzo R., Prandoni I., Shulevski A., Tasse C., Vaccari M.,
Zarka P., Roettgering H.
<Astron. Astrophys. 648, A104 (2021)>
=2021A&A...648A.104D 2021A&A...648A.104D (SIMBAD/NED BibCode)
ADC_Keywords: Surveys ; Radio sources ; Radio continuum
Keywords: surveys - catalogs - radio continuum: general -
techniques: image processing
Abstract:
LOFAR is the only radio telescope that is presently capable of
high-sensitivity, high-resolution (i.e. <1mJy/b and <15") observations
at ultra-low frequencies (<100MHz). To utilise these capabilities, the
LOFAR Surveys Key Science Project is undertaking a large survey to
cover the entire northern sky with Low Band Antenna (LBA)
observations.
The LOFAR LBA Sky Survey (LoLSS) aims to cover the entire northern sky
with 3170 pointings in the frequency range 42-66MHz, at a resolution
of 15-arcsec and at a sensitivity of 1mJy/beam (1σ. Here we
outline the survey strategy, the observational status, the current
calibration techniques, and briefly describe several scientific
motivations. We also describe the preliminary public data release.
The preliminary images were produced using a fully automated pipeline
that aims to correct all direction-independent effects in the data.
Whilst the direction-dependent effects, such as those from the
ionosphere, are not yet corrected, the images presented in this work
are still 10 times more sensitive than previous surveys available at
these low frequencies.
The preliminary data release covers 740deg2 around the HETDEX spring
field region at a resolution of 47" with a median noise level of
5mJy/beam. The images and the catalogue with 25247 sources are publicly
released. We demonstrate that the system is capable of reaching an rms
noise of 1mJy/beam and the resolution of 15" once direction-dependent
effects are corrected for.
LoLSS will provide the ultra-low-frequency information for hundreds of
thousands of radio sources, providing critical spectral information
and producing a unique dataset that can be used for a wide range of
science topics such as: the search for high redshift galaxies and
quasars, the study of the magnetosphere of exoplanets, and the
detection of the oldest populations of cosmic-rays in galaxies,
clusters of galaxies, and from AGN activity.
Description:
Preliminary release of the LOFAR LBA Sky Survey. The catalogue
contains 25247 radio sources detected in the HETDEX Spring field at
45MHz. The survey has a median sensitivity of 4mJy/beam with an
angular resolution of 47-arcsec.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
lolssv3.dat 264 25247 LOFAR LBA Sky Survey preliminary release catalog
list.dat 81 1 Information on fits image
fits/* . 1 Fits image
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Byte-by-byte Description of file: lolssv3.dat
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Bytes Format Units Label Explanations
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1- 20 A20 --- Name Source ID (LOLpJHHMMSS.s+DDMMSS)
22- 36 F15.11 deg RAdeg Right ascension (J2000)
38- 46 F9.6 arcsec e_RAdeg Error on the Right ascension
48- 62 F15.11 deg DEdeg Declination (J2000)
64- 72 F9.6 arcsec e_DEdeg Error on the Declination
74- 85 E12.6 mJy TotalFlux Integrated flux density
87- 98 E12.6 mJy e_TotalFlux Error on the integrated flux density
100-111 E12.6 mJy/beam PeakFlux Peak brightness, affected by smearing
113-124 E12.6 mJy/beam e_PeakFlux Error on the peak brightness
126-135 F10.6 arcsec Maj Source size, major axis
137-145 F9.6 arcsec e_Maj Error on the major axis
147-156 F10.6 arcsec Min Source size, minor axis
158-166 F9.6 arcsec e_Min Error on the minor axis
168-177 F10.6 deg PA Position angle
179-188 F10.6 deg e_PA Error on the position angle
190-199 F10.6 arcsec DCMaj Deconvolved source size, major axis
201-209 F9.6 arcsec e_DCMaj Error on the deconvolved major axis
211-220 F10.6 arcsec DCMin Deconvolved source size, minor axis
222-230 F9.6 arcsec e_DCMin Error on the deconvolved minor axis
232-241 F10.6 deg DCPA Deconvolved position angle
243-252 F10.6 deg e_DCPA Error on the deconvolved position angle
254-262 F9.5 mJy/beam Islrms Local rms noise
264 A1 --- SCode [CMS] Source code (1)
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Note (1): Source structure code as follows:
S = for single Gaussian
M = for multiple Gaussian
C = single-Gaussian source in an island with other sources
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 24 I5 --- Nx Number of pixels along X-axis
26- 29 I4 --- Ny Number of pixels along Y-axis
31- 37 I7 Kibyte size Size of FITS file
39- 54 A16 --- FileName Name of FITS file, in subdirectory fits
56- 81 A26 --- Title Title of the FITS file
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Acknowledgements:
Francesco de Gasperin, fdg(at)hs.uni-hamburg.de
(End) Patricia Vannier [CDS] 15-Feb-2021