ACDS V10.0 - Detailed Description of VIII/40

ACDS V10.0 - Sun Jan 19 06:26:15 CET 2025

| # Detailed Description of VIII/40 : GB6 catalog of radio sources (Gregory+ 1996) |

Note : this is the description file of the original catalog. This HTML page corresponds well to the original description, but some minor changes in the format may have been introduced in the FITS output files in order to allow for arithmetic operations on quantities such as coordinates and times. h:m:s and d:m:s units are normally converted into degrees, and YYYY-MM-DD into julian days.
Similarly, some slight changes may have been introduced in the units; the value given in the HTML files supersedes the value indicated in the ReadMe file for this catalogue.

    VIII/40            GB6 catalog of radio sources        (Gregory+ 1996)
    ================================================================================
    The GB6 catalog of radio sources
         Gregory P.C., Scott W.K., Douglas K., Condon J.J.
        <Astrophys. J. Suppl. Ser. 103, 427 (1996)>
        =1996ApJS..103..427G
    ================================================================================
    ADC_Keywords: Radio sources

    Keywords: catalogs - radio continuum: galaxies - surveys

    Abstract:
        The Green Bank 4.85GHz (lambda~6cm) survey was made with the NRAO
        seven-beam receiver on the (former) 91m telescope during 1986
        November and 1987 October. The final set of sky maps covering the
        declination band 0deg<Dec.<+75deg was constructed with data from
        both epochs. Its noise and position errors are nearly a factor of
        2(1/2) smaller than in the epoch 1987 maps, from which the 87GB
        catalog VIII/14 of 54,579 sources stronger than S~25mJy was
        extracted. Therefore, we used the new maps to make the GB6 catalog of
        75,162 discrete sources with angular sizes phi<=10.5arcmin and flux
        densities S>=18mJy. This catalog is available in machine-readable
        versions with either B1950 or J2000 positions and as a printed book
        with B1950 positions. The GB6 weighted differential source counts
        S^(5/2)n(S) between 18 mJy and 7Jy agree well with evolutionary models
        based on independent data.

    Description:
        The final set of sky maps from the Green Bank 4.85 GHz survey
        (Condon J.J., Broderick J.J., Seielstad G.A., Douglas K., &
        Gregory P.C. in 1994AJ....107.1829C) was used to construct the GB6
        Catalog of sources stronger than S ~ 18 mJy in the declination range
        0deg < Dec. < +75deg (Gregory P.C., Scott W.K., Douglas K., &
        Condon J.J. in 1996ApJS..103..427G). There are two machine-readable
        versions of the GB6 catalog, with coordinates precessed to B1950
        (file b1950.dat) and J2000 (file j2000.dat). Each catalog file
        contains one line per source (75,162 lines each), and the sources are
        sorted by increasing B1950 or J2000 right ascension.

    File Summary:

           FileName      Lrecl  Records   Explanations

    ×                   80        .   This file
    × ReadMe            80        .   This file
    × gb6.dat          117    75162   GB6 catalog, merged J2000/B1950
    × b1950.dat         95    75162   GB6 catalog, B1950 coordinates
    × j2000.dat         95    75162   GB6 catalog, J2000 coordinates

    See also:
        VIII/14 : 87GB Catalog of radio sources (Gregory et al., 1991)
        VIII/38 : The PMN Surveys at 4.85GHz (Griffith+ 1993-1996)

    Byte-by-byte Description of file:  gb6.dat

       Bytes Format Units   Label     Explanations

       1-  2  I2    h       RAh       Right ascension (J2000)
       3-  4  I2    min     RAm       Right ascension (J2000)
       5-  8  F4.1  s       RAs       Right ascension (J2000)
       9- 12  F4.1  s       e_RAs     Uncertainty in R.A.
          14  A1    ---     DE-       Sign of declination (J2000)
      15- 16  I2    deg     DEd       Declination (J2000)
      17- 18  I2    arcmin  DEm       Declination (J2000)
      19- 20  I2    arcsec  DEs       Declination (J2000)
      22- 23  I2    arcsec  e_DEs     Uncertainty in declination
      25- 29  F5.1  deg     GLAT      Galactic latitude
      31- 35  F5.1  deg     GLON      Galactic longitude
      37- 41  I5    mJy     Flux      4.85 GHz peak flux density
      43- 46  I4    mJy     e_Flux    Uncertainty in peak flux density
          48  A1    ---     Bflag     [B] for sources near the border (1)
          49  A1    ---     Eflag     [E] for significant extension
          50  A1    ---     Wflag     [W] for warning (weak source with
                                            large Zero)
          51  A1    ---     Cflag     [C] for confusion (near a stronger source)
      53- 56  F4.2  ---     MajAxis   Normalized FWHM major axis / beam size
      58- 61  F4.2  ---     MinAxis   Normalized FWHM minor axis / beam size
      63- 65  I3    deg     PA        [-90/90] Fitted major axis position angle
                                        (degrees east of north)
      67- 69  I3    mJy     Zero      Local sky level, Z / beam
      71- 74  I4    pix     Xmap      Map pixel column number (from left)
      76- 79  I4    pix     Ymap      Map pixel row number (from bottom)
      81- 91  A11   ---     GB6       Name (based on J2000 position) (2)
      92-102  A11   ---     GB6(B)    Name based on B1950 position (2)
     103-104  I2    h       RA1950h   Right Ascension B1950 (hours)
     105-106  I2    min     RA1950m   Right Ascension B1950 (minutes)
     107-110  F4.1  s       RA1950s   Right Ascension B1950 (seconds)
         111  A1    ---     DE1950-   Declination B1950 (sign)
     112-113  I2    deg     DE1950d   Declination B1950 (degrees)
     114-115  I2    arcmin  DE1950m   Declination B1950 (minutes)
     116-117  I2    arcsec  DE1950s   Declination B1950 (seconds)

    Note (1): The GB6 catalog is the result of merging 288 catalogs,
        each of which came from a single GB6 image covering about 15X15deg of
        sky. Sources found near the border of an image are flagged 'B'. The
        borders of these images overlap, so duplication among sources which
        appeared in two or more catalogs had to be removed from the final GB6
        catalog. Normally, the one fit without the 'B' flag was chosen. Thus
        there are two classes of 'B' sources which remain in the final
        catalog:
        (1) All sources near the upper (+75 deg) and lower (0 deg) declination
        limits of the images.
        (2) Sources elsewhere that are just at the catalog limit, so the fit
        was just above the limit near the border of one image and just below
        the limit in the overlapping image(s).
    Note (2): the names are made from the position truncated to the minute
        in right ascension and arcminute in declination; in case of name
        collision (sources falling in the same truncated RA/Dec box), a
        lowercase letter was appended to the name in order of right
        ascension, according to section 3 of the paper.

    Byte-by-byte Description of file:  b1950.dat  j2000.dat

       Bytes Format  Units     Label    Explanations

       1-  2  I2     h         RAh      Right ascension (B1950 or J2000)
       3-  4  I2     min       RAm      Right ascension
       5-  8  F4.1   s         RAs      Right ascension
       9- 12  F4.1   s         e_RAs    Uncertainty in R.A.
          14  A1     ---       DE-      Sign of declination
      15- 16  I2     deg       DEd      Declination (B1950 or J2000)
      17- 18  I2     arcmin    DEm      Declination
      19- 20  I2     arcsec    DEs      Declination
      22- 23  I2     arcsec    e_DEs    Uncertainty in declination
      25- 29  F5.1   deg       GLAT     Galactic latitude
      31- 35  F5.1   deg       GLON     Galactic longitude
      37- 41  I5     mJy       Flux     4.85 GHz peak flux density
      43- 46  I4     mJy       e_Flux   Uncertainty in peak flux density
          48  A1     ---       Bflag    [B] near border, see Note (1) above
          49  A1     ---       Eflag    [E] for significant extension
          50  A1     ---       Wflag    [W] for warning (weak source with
                                            large Zero)
          51  A1     ---       Cflag    [C] for confusion (near a stronger source)
      53- 56  F4.2   ---       MajAxis  Normalized FWHM major axis / beam size
      58- 61  F4.2   ---       MinAxis  Normalized FWHM minor axis / beam size
      63- 65  I3     deg       PA       [-90/90] Fitted major axis position angle
                                        (degrees east of north)
      67- 69  I3     mJy       Zero     Local sky level, Z / beam
      71- 74  I4     pix       Xmap     Map pixel column number (from left)
      76- 79  I4     pix       Ymap     Map pixel row number (from bottom)
      81- 95  A15    ---       Name     Name of source (based on position)

    Remarks:
       If you would like to order the printed catalog or have any questions,
       comments, or special requests, please contact Jim Condon by e-mail at
       Internet address jcondon@nrao.edu.

    History:
        The tables b1950.dat and j2000.dat were first published on the AAS
        AAS CD-ROM series, Volume 6, 1996, directory volume6/apjs/v103/p427;
        the source names, which were not included on the CD-ROM, were kindly
        supplied to CDS by Jim Condon (jcondon@nrao.edu) in December 1996.
        The merged file (gb6.dat) was generated at CDS, and is in the same
        order as j2000.dat
      * 06-Feb-2004: in the file "gb6.dat", the suffix letter used to
        distinguish sources falling in the same "name box" was converted
        from its uppercase form to lowercase, in order to comply to
        section 3 of the paper.
    ================================================================================
    (End)                                     Francois Ochsenbein [CDS]  07-Jan-1997