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GB6 - Green Bank 6-cm (GB6) Radio Source Catalog

HEASARC
Archive

Overview

This table contains the Green Bank 6-cm (GB6) Radio Source Catalog. The Green Bank 4.85 GHz (6-cm wavelength) survey (Condon J.J., Broderick J.J., Seielstad G.A., Douglas K., & Gregory P.C. in 1994AJ....107.1829C) 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 0 deg < Dec. < +75 deg 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 (CDS Catalog <VIII/14>) of 54,579 sources stronger than S ~ 25mJy was extracted. Therefore, the new maps were used to make the GB6 catalog of 75,162 discrete sources with angular sizes phi <= 10.5 arcmin and flux densities S >= 18mJy. The GB6 weighted differential source counts S^(5/2)n(S) between 18 mJy and 7 Jy agree well with evolutionary models based on independent data.

Catalog Bibcode

1996ApJS..103..427G

References

     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

Provenance

This table was created by the HEASARC in July 2003 based on CDS Catalog <VIII/40>.

Parameters

Name
The GB6 source designation based on the J2000 position.

RA
The Right Ascension of the radio source in the selected equinox. This was given to a precision of 0.1 seconds of time in the original table.

Dec
The Declination of the radio source in the selected equinox. This was given to a precision of 1 arcsecond in the original table.

LII
The Galactic Longitude of the radio source.

BII
The Galactic Latitude of the radio source.

RA_Error
The rms uncertainty in the Right Ascension, in seconds of time.

Dec_Error
The rms uncertainty in the Declination, in arcseconds.

Flux_6_cm
The 4.85-GHz peak flux density, in mJy.

Flux_6_cm_Error
The rms uncertainty in the 4.85-GHz peak flux density, in mJy.

Border_Flag
A flag parameter which is set to "B" to indicate that the source is near the border of an image. The GB6 Catalog is the result of merging 288 catalogs, each of which came from a single GB6 image covering about 15 X 15 deg 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, and (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).

Extent_Flag
A flag parameter which is set to "E" to indicate that there is either significant extension to the source, or that it is a partially resolved blend of two or more point sources.

Weak_Flag
A flag parameter which is set to "W" to indicate a warning for a weak source with large zero offset |Z|, narrow fitted minor axis < 0.60 * the minor axis of the beam size, or very bad confusion, less reliable than most.

Confusion_Flag
A flag parameter which is set to "C" to indicate that this is a confused source near a stronger source or its sidelobes.

Major_Axis
The dimensionless angular size of the radio source, given as the normalized FWHM major axis in units of the beam size major axis (the major diameter of the point source response).

Minor_Axis
The dimensionless angular size of the radio source, given as the normalized FWHM minor axis in units of the beam size minor axis (the minor diameter of the point source response).

Position_Angle
The fitted major axis position angle, in degrees east of north.

Zero_Level
The local zero level Z, in mJy/beam.

X_Pixel
The map pixel column number of the radio source, measured from the left.

Y_Pixel
The map pixel row number of the radio source, measured from the bottom.


Contact Person

Questions regarding the GB6 database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 8-Nov-2004