========================================================================== VIII/97 74MHz VLA Low-frequency Sky Survey Redux (VLSSr) (Lane+, 2014) The following files can be converted to FITS (extension .fit or fit.gz) table1.dat catalog.dat ========================================================================== Query from: http://vizier.u-strasbg.fr/viz-bin/VizieR?-source=VIII/97 ==========================================================================
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Beginning of ReadMe : VIII/97 74MHz VLA Low-frequency Sky Survey Redux (VLSSr) (Lane+, 2014) ================================================================================ The Very Large Array Low-frequency Sky Survey Redux (VLSSr). Lane W.M., Cotton W.D., van Velzen S., Clarke T.E., Kassim N.E., Helmboldt J.F., Lazio T.J.W., Cohen A.S. <Mon. Not. R. Astron. Soc., 440, 327-338 (2014)> =2014MNRAS.440..327L ================================================================================ ADC_Keywords: Radio continuum ; Radio sources ; Surveys Keywords: techniques: image processing; catalogues; surveys; radio continuum: general Abstract: We present the results of a recent re-reduction of the data from the Very Large Array (VLA) Low-frequency Sky Survey (VLSS). We used the VLSS catalogue as a sky model to correct the ionospheric distortions in the data and create a new set of sky maps and corresponding catalogue at 73.8MHz. The VLSS Redux (VLSSr) has a resolution of 75", and an average map rms noise level of sigma 0.1Jy/beam. The clean bias is 0.66xsigma and the theoretical largest angular size is 36'. Six previously unimaged fields are included in the VLSSr, which has an unbroken sky coverage over 9.3sr above an irregular southern boundary. The final catalogue includes 92964 sources. The VLSSr improves upon the original VLSS in a number of areas including imaging of large sources, image sensitivity, and clean bias; however the most critical improvement is the replacement of an inaccurate primary beam correction which caused source flux errors which vary as a function of radius to nearest pointing centre in the VLSS. Description: The VLSSr reprocessed all of the data from the original VLSS project. The observations were made between 2001 and 2007, under VLA observing programs AP397, AP441, AP452, and AP509. The sky was divided into a roughly hexagonal grid of 523 pointing centres, at a spacing of 8.6deg. The bandwidth used was 1.56MHz centred at 73.8MHz. Fields in the range -10<DEC<80deg were observed in the VLA B configuration, while those at DEC<-10deg and DEC>80deg were observed in the BnA configuration to compensate for beam elongation at low elevations. Further details of the observational setup are given in Cohen et al. (VLSS; 2007, Cat. VIII/79). The final catalogue contains 92964 entries. Of these, roughly 3 per cent have no match in the NVSS within 60 arcsec of the fitted position. However many unmatched sources are actually components of larger sources which may be fit differently in the two catalogues. The global rms position error is 3.3 arcsec in RA and 3.5 arcsec in declination.