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J/A+A/598/A78       The GMRT 150MHz all-sky radio survey         (Intema+, 2017)

The GMRT 150 MHz all-sky radio survey. First alternative data release TGSS ADR1. Intema H.T., Jagannathan P., Mooley K., Frail D.A. <Astron. Astrophys. 598, A78 (2017)> =2017A&A...598A..78I (SIMBAD/NED BibCode)
ADC_Keywords: Surveys ; Radio continuum Keywords: surveys - catalogs - radio continuum: general - techniques: image processing Abstract: We present the first full release of a survey of the 150MHz radio sky, observed with the Giant Metrewave Radio Telescope (GMRT) between April 2010 and March 2012 as part of the TIFR GMRT Sky Survey (TGSS) project. Aimed at producing a reliable compact source survey, our automated data reduction pipeline efficiently processed more than 2000h of observations with minimal human interaction. Through application of innovative techniques such as image-based flagging, direction-dependent calibration of ionospheric phase errors, correcting for systematic offsets in antenna pointing, and improving the primary beam model, we created good quality images for over 95 percent of the 5336 pointings. Our data release covers 36900deg2 (or 3.6πsteradians) of the sky between -53° and +90° declination (Dec), which is 90 percent of the total sky. The majority of pointing images have a noise level below 5mJy/beam with an approximate resolution of 25"x25" (or 25"x25"/cos(Dec-19°) for pointings south of 19° declination). We have produced a catalog of 0.62 Million radio sources derived from an initial, high reliability source extraction at the seven sigma level. For the bulk of the survey, the measured overall astrometric accuracy is better than two arcseconds in right ascension and declination, while the flux density accuracy is estimated at approximately ten percent. Within the scope of the TGSS alternative data release (TGSS ADR) project, the source catalog, as well as 5336 mosaic images (5°x5°) and an image cutout service, are made publicly available at the CDS as a service to the astronomical community. Next to enabling a wide range of different scientific investigations, we anticipate that these survey products will provide a solid reference for various new low-frequency radio aperture array telescopes (LOFAR, LWA, MWA, SKA-low), and can play an important role in characterizing the epoch-of-reionisation (EoR) foreground. The TGSS ADR project aims at continuously improving the quality of the survey data products. Near-future improvements include replacement of bright source snapshot images with archival targeted observations, using new observations to fill the holes in sky coverage and replace very poor quality observational data, and an improved flux calibration strategy for less severely affected observational data. Description: We provide the first full public release of the 150 MHz continuum survey (TGSS) from the Giant Metrewave Radio Telescope. The resulting images cover the full sky north of DEC -53 degrees (or 36,900 square degrees) with a median RMS background noise of 3.5mJy per beam and a typical resolution of 25". Our final radio source catalog contains 0.62 million sources with flux densities ranging from 11.1mJy to 9.22kJy. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table3.dat 149 623604 Full source catalog of TGSS ADR1 150 MHz sources
Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
1- 16 A16 --- TGSSADR Name without prefix (JHHMMSS.S+DDMMSS) (1) 19- 27 F9.5 deg RAdeg Centroid right ascension (J2000) 30- 33 F4.1 arcsec e_RAdeg Uncertainty on right ascension (1 sigma) 36- 44 F9.5 deg DEdeg Centroid declination (J2000) 47- 50 F4.1 arcsec e_DEdeg Uncertainty on declination (1 sigma) 53- 61 F9.1 mJy Stotal Total (integrated) flux density at 150MHz 64- 71 F8.1 mJy e_Stotal Uncertainty on Stotal (1 sigma) 74- 82 F9.1 mJy/beam Speak Peak flux at 150MHz 85- 92 F8.1 mJy/beam e_Speak Uncertainty on Speak (1 sigma) 95- 99 F5.1 arcsec Maj Gaussian fit major axis 102-105 F4.1 arcsec e_Maj Uncertainty on Maj (1 sigma) 108-112 F5.1 arcsec Min Gaussian fit minor axis 115-118 F4.1 arcsec e_Min Uncertainty on Min (1 sigma) 121-125 F5.1 deg PA [] Gaussian fit position angle (2) 128-131 F4.1 deg e_PA Uncertainty on PA (1 sigma) 133-138 F6.1 mJy/beam Noise Local image background RMS noise 141 A1 --- Code [SCM] Source structure code (S/C/M) (3) 144-149 A6 --- Mosaic Name of parent mosaic image (4)
Note (1): The full source name including prefix is 'TGSSADR JHHMMSS.S+DDMMSS', with HHMMSS.S+DDMMSS the centroid coordinates in sexagesimal format following the IAU truncation standard. Note (2): The PA uncertainty is clipped at 90 degrees, which indicates an undetermined PA (e.g. a circular beam). Note (3): The source structure code defines the multiplicity of the source structure in terms of Gaussian components as follows: S = refers to an isolated single-Gaussian source C = refers to a single-Gaussian source partly overlapping with other sources M = is a source fit with multiple Gaussians Note (4): The parent image mosaic is the 5x5 deg2 image from which the source entry is extracted. Mosaic names are formatted as 'RxxDyy', with xx being a zero-padded RA index running from 01 to 72, and yy a zero-padded DEC index running from 00 to 85. A list of mosaic names and their center coordinates is provided through the TGSS ADR project website: http://tgssadr.strw.leidenuniv.nl
Acknowledgements: Huib Intema, intema(at)strw.leidenuniv.nl
(End) Huib Intema [Leiden Obs./NRAO], Patricia Vannier [CDS] 05-Dec-2016
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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