ACDS V10.0 - Thu May 02 22:29:58 CEST 2019
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Detailed Description of VIII/40 :
GB6 catalog of radio sources (Gregory+ 1996)
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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)
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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
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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.
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(End) Francois Ochsenbein [CDS] 07-Jan-1997