The 6C Survey of Radio Sources - IV.
The Zone 67 deg < Dec < 82 deg, 0h < RA < 24h
Hales, Mayer, Warner and Baldwin (1991)
Documentation for the Computer-Readable Version
N. A. Oliversen
Doc. No. NSSDC/WDC-A-R&S 93-26
July 1993
National Space Science Data Center (NSSDC)/
World Data Center A for Rockets and Satellites (WDC-A-R&S)
National Aeronautics and Space Administration
Goddard Space Flight Center
Greenbelt, Maryland 20771
Abstract
This catalogue contains the fourth section of the 6C Cambridge survey
of radio sources at 151 MHz, covering the region from 67 deg to 82 deg
in declination and between 0h and 24h in right ascension. The survey
has an angular resolution of 4.02 x 4.02 x cosec(dec). Data include the
source positions (B1950), peak flux density, integrated flux density,
contour map panel number and contour map field names. The limiting flux
density is 160 mJy at 151 MHz in the present zone with completeness
achieved at 400 mJy on the best maps and at about 800 mJy on the worst.
This part of the survey contains 5421 sources, covering an area of 1440
square degrees.
1 - Introduction
A copy of this document should be distributed with every copy of the
machine-readable catalog.
1.1 - Description
"The 6C Survey of Radio Sources - IV. The Zone 67 deg < Dec < 82 deg,
0h < RA < 24h" (6CSRSIV) contains a compilation of radio source
oservations made with the use of an (non-tracking) Earth- rotation
aperture synthesis telescope comprising many small aerial arrays on an
east-west baseline operating at 151 MHz. This paper is the fourth in a
series: Details on the design and operation of the telescope and the
reduction of the survey were first discussed in Baldwin et al. (1985).
Other papers in the series include Hales et al. (1988) and Hales et al.
(1990). The present zone overlaps that covered in Baldwin et al.
(1985) over the range 80 deg < Dec < 82 deg and also that covered in
Hales et al. (1990) over the range 67 deg < Dec < 68 deg and 5h 25m <
RA < 18h 17m.
The catalogue contains a listing of 5421 radio sources ordered by
increasing right ascension from 0h to 24h. The survey is centered on a
declination of 75 deg and includes from declination 67 deg to 82 deg.
Eight fields have been included in this survey: 0100+75, 0400+75,
0700+75, 1000+75, 1300+75, 1600+75, 1900+75, and 2200+75.
Attenuation corrections were applied to all flux densities and maps
using tables derived for each synthesis (see Hales et al. 1988). Flux
densities are on the scale of Roger, Bridle and Costain (1973) (RBC).
The authors believe the flux density scale is consistent with the RBC
scale to within +/-5%. See 6CSRSIV and Baldwin et al. (1985) for
details on source selection criterion and error analysis.
Source positions have been adjusted (by 2.8s to 5.5s in right ascension
and by up to 1100 in declination) to agree with known positions of
bright sources. The residual rms scatter in the corrected positions of
the reference sources relative to their true positions is estimated to
be +/- 3 to 5'' in each coordinate. See 6CSRSIV for details.
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Note that this file only contains the catalogue of radio sources. It
is intended to be used with the radio maps originally published on
microfiche in Hales, Mayer, Warner and Baldwin (1991). The source
lists and FITS format maps for the four regions of the 6C survey
published to date have been placed on a CDROM entitled "Images from the
Radio Universe", which is available from the address below. A nominal
fee may be charged for such requests.
Prof. Jim Condon
NRAO
Edgemont Road
Charlottesville, Virginia 22903-2475
1.2 - Reference
Hales, S.E.G., Mayer, C.J., Warner, P.J. and Balwin J.E. 1991, MNRAS,
251, 46.
2 - Structure
2.1 - The File as a Whole
"The 6C Survey of Radio Sources - IV. The Zone 67 deg < Dec < 82 deg,
0h < RA < 24h " consists of a single fixed-block file of 5421 50-byte
records. The original file was variable format with 49-bytes per
record. Detailed descriptions of some of the fields in the file are
given in the following sections.
2.2 - Catalog File
Bytes Units Format Item
1 - 2 h I2 Right ascension (B1950)
4 - 5 min I2 Right ascension (B1950)
7 - 10 s F4.1 Right ascension (B1950)
12 - 14 deg I3 Declination (B1950)
16 - 17 ' I2 Declination (B1950)
19 - 20 '' I2 Declination (B1950)
23 - 27 Jy F5.2 Flux density (peak)
30 - 34 Jy F5.2 Flux density (integ.)
38 - 39 I2 Contour map panel number
41 A1 The character ":"
43 - 49 A7 Contour map field name
Table 1: Catalog Record Format
Flux density (peak): Source peak flux density at 151 MHz.
2
Flux density (integrated): Source integrated flux density at 151 MHz.
Integrated flux densities were carried out for sources with apparent
flux densities above 513 mJy. The integration was carried out to a
limiting level of 10% of the fitted peak (or for 110 mJy for sources
having apparent flux densities < 1.10 Jy). For the right-half of the
field 1900+75, the threshold to qualify for integration was raised to
1.54 Jy and for the apex of the field 2200+75, to 0.96 Jy, with
limiting level for both cases of 10% (or 154 mJy for sources having
apparent peak flux densities < 1.54 Jy). Note that for unresolved
sources the integrated flux value can fall below the peak value. If
the column is marked with a dash (-), the peak flux was not strong
enough to calculate the integrated flux. If the column is marked with
an asterisk (*), the peak flux was strong enough to qualify for
integration, but it has been integrated into a brighter adjoining peak.
Contour map panel number: This column contains the panel number of the
contour map in which the source appears in the survey. The number of
contour panels per map field varies from 27 to 32. The panel number
and the map field name tell the user where to look up the source of
interest in the published contour map.
Contour map field name: This column contains the name of the field in
which the source appears. Eight fields have been included in this
survey: 0100+75, 0400+75, 0700+75, 1000+75, 1300+75, 1600+75, 1900+75,
and 2200+75. The panel number and the map field name tell the user
where to look up the source of interest in the published contour map.
3 - History
3.1 - Remarks and Modification
"The 6C Survey of Radio Sources - IV. The Zone 67 deg < Dec < 82 deg,
0h < RA < 24h " was received by the Astronomical Data Center (ADC),
NASA Goddard Space Flight Center, from Dr. Heinz Andernach of
Instituto de Astrofisica de Canarias, IAC, Tenerife, Spain.
4 - Reference to the Documentation
Baldwin, J.E., Boysen, R.C., Hales, S.E.G., Jennings, J.E., Waggett,
P.C., Warner, P.J. and Wilson, D.M.A. 1985, MNRAS, 217, 717
Hales, S.E.G., Baldwin, J.E. and Warner, P.J. 1988, MNRAS, 234, 919
Hales, S.E.G. 1990, MNRAS, 246, 256
Hales, S.E.G. 1991, MNRAS, 251, 46
Roger, R.S., Bridle, A.H. and Costain, C.H. 1973, AJ, 78, 1030
3