Access to Astronomical Catalogues

← Click to display the menu
VIII/72               CLASS survey of radio sources               (Myers+, 2003)

The Cosmic Lens All Sky Survey. I. Source selection and observations. Myers S.T., Jackson N.J., Browne I.W.A., de Bruyn A.G., Pearson T.J., Readhead A.C.S., Wilkinson P.N., Biggs A.D., Blandford R.D., Fassnacht C.D., Koopmans L.V.E., Marlow D.R., McKean J.P., Norbury M.A., Phillips P.M., Rusin D., Shepherd M.C., Sykes C.M. <Mon. Not. R. Astron. Soc. 341, 1 (2003)> =2003MNRAS.341....1M II. Gravitational lens candidate selection and follow-up. <Mon. Not. R. Astron. Soc. 341, 13 (2003)> =2003MNRAS.341...13B
ADC_Keywords: Radio sources Keywords: cosmology ; gravitational lensing Abstract: The Cosmic Lens All-Sky Survey (CLASS) is an international collaborative program aimed at obtaining high-resolution radio images of over 10000 flat-spectrum radio sources in order to create the largest and best studied statistical sample of radio-loud gravitationally lensed systems. CLASS is aimed at identifying lenses where multiple images are formed from compact flat-spectrum radio sources, which should be easily identifiable in the radio maps (Browne et al., 2003MNRAS.341...13B). In four observing ``seasons'' from 1994-1999, CLASS has observed 13832 radio sources. When combined with the JVAS survey, the CLASS sample contains over 16,000 images. Using the GB6 and NVSS surveys, a complete statistical subset of 11685 sources has been constructed. These were selected from the NVSS 20-cm (Condon et al., 1998, Cat. VIII/65) and GB6 6-cm (Gregory et al., 1996, Cat. VIII/40) catalogues by the selection criteria: declination >0deg, |b|<10deg, S(6cm)≥30mJy, and spectral index between 6 and 20cm flatter than -0.5 (S proportional to frequency+alpha). The remaining sources were selected using earlier versions of these catalogues or with slightly relaxed versions of these criteria. Introduction: The data in this table were assembled from pointings at 16503 radio sources in the JVAS and CLASS surveys between 1990 and 1999 using the VLA in A-configuration at 8.4GHz. The resolution is approximately 220 milliarcsec. The data were mapped using an automatic DIFMAP script (Shepherd et al., 1997, ASP Conference Series, 125, 77) which located the brightest radio source within a 2' by 2' box around the pointing position, and searched for all subsidiary components within a 70"x70" box around the brightest source. Sources were regarded as not detected if no component of 5mJy or more was visible in the initial search box. Except in cases of bad data or complicated sources, the positions of primary sources of 30mJy or above are accurate to about 40mas. More details of the process are given in the paper (2003MNRAS.341....1M) File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file catalog.dat 129 23418 CLASS catalog
See also: VIII/65 : 1.4GHz NRAO VLA Sky Survey (NVSS) (Condon+ 1998) VIII/40 : GB6 catalog of radio sources (Gregory+ 1996) : Paper HomePage Byte-by-byte Description of file: catalog.dat
Bytes Format Units Label Explanations
1- 4 A4 --- --- [GB6J] 5- 17 A13 --- GB6 Name from the Greenbank 6-cm catalogue Gregory et al., 1996, Cat. VIII/40 19- 26 A8 --- Obsname Name in the VLA observation list 28- 31 F4.2 --- qin ? Quality indicator of map (1) 33- 34 I2 h RAph ? Pointing position Right Ascension J2000 36- 37 I2 min RApm ? Pointing position Right Ascension J2000 39- 43 F5.2 s RAps ? Pointing position Right Ascension J2000 46 A1 --- DEp- ? Pointing position Declination sign 47- 48 I2 deg DEpd ? Pointing position Declination J2000 50- 51 I2 arcmin DEpm ? Pointing position Declination J2000 53- 56 F4.1 arcsec DEps ? Pointing position Declination J2000 61- 71 A11 --- dir Data directory of observing epoch (2) 75- 76 I2 h RAh ? Component position Right Ascension J2000 (3) 78- 79 I2 min RAm ? Component position Right Ascension J2000 (3) 81- 87 F7.4 s RAs ? Component position Right Ascension J2000 (3) 90 A1 --- DE- ? Component position Declination sign (3) 91- 92 I2 deg DEd ? Component position Declination J2000 (3) 94- 95 I2 arcmin DEm ? Component position Declination J2000 (3) 97-102 F6.3 arcsec DEs ? Component position Declination J2000 (3) 104-112 F9.1 mJy S8.4GHz ? 8.4GHz flux density of component (3) 114-119 I6 mas maj ? Fitted major axis of component (3) 121-124 F4.2 --- b/a [0,1]? Fitted axis ratio of resolved components (3) (4) 126-129 I4 deg PA [-90/90]? Position angle fitted to component (3)
Note (1): This is defined as the ratio of the flux density of the brightest component in the radio map, divided by the initial peak in the residual map before self-calibration. It serves as a rough quality control, as the data were processed using an automatic DIFMAP script without human intervention. In an ideal case the ratio should be 1. In cases where the number is 1.5 or greater, the map may contain spurious radio structure and the original data should be consulted. A blank field indicates a non-detection Note (2): Observing epoch: 90-92 = JVAS 94 = CLASS1 95 = CLASS2 98 = CLASS3 99 = CLASS4 Note (3): These data are repeated for each radio component detected in an observation. Note (4): This is produced by the DIFMAP modelfit software. In cases where the component is not significantly resolved the axis ratio is set to 0.00.

(End) Neal Jackson [Jodrell Bank Obs.] 10-Feb-2003
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

catalogue service