VIII/4 Fourth Cambridge Survey (4C) (Pilkington+ 1965; Gower+ 1967)
A survey of radio sources between declinations 20 and 40.
Pilkington J.D.H., Scott P.F.
<Mem. Roy. Astron. Soc. 69, 183 (1965)>
=1965MmRAS..69..183P 1965MmRAS..69..183P
A survey of radio sources in the declination ranges -07 to 20 and 40 to 80.
Gower J.F.R., Scott P.F., Wills D.
<Mem. Roy. Astron. Soc. 71, 49 (1967)>
=1967MmRAS..71...49G 1967MmRAS..71...49G
ADC_Keywords: Surveys; Radio sources
Description:
The Fourth Cambridge Radio Survey (4C) Catalogue contains all survey
data from the papers of Pilkington and Scott (1965MmRAS..69..183P 1965MmRAS..69..183P) and
Gower, Scott and Wills (1967MmRAS..71...49G 1967MmRAS..71...49G). These data result from a
survey of radio sources between declinations -07 and +80 degrees using
the large Cambridge interferometer at 178 MHz. The computerized
catalog contains for each source the 4C number, 1950 position,
measured flux density, accuracy class, galactic coordinates, and
remarks. For some sources miscellaneous brief comments such as cross
identifications to the 3C catalog or remarks on contamination from
nearby sources are given at the ends of the data records. A flag (*)
is included if there are additional remarks in the published catalog.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
radio4c.dat 72 4844 Fourth Cambridge Radio Survey Data
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Byte-by-byte Description of file: radio4c.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- 4C *The 4C number
11-12 I2 h RAh *Right ascension equinox 1950.0
14-15 I2 min RAm R.A. in minutes
17-20 F4.1 s RAs R.A. in seconds
23 A1 --- DE- Sign of declination equinox 1950.0
24-25 I2 deg DEd Dec.
27-30 F4.1 arcmin DEm Dec.
34-40 F7.1 Jy FluxDen *Flux density (1.0E-26 W/m2/Hz) at 178MHz
43-44 I2 --- ErrClas1 *Position and flux error class (in number)
48-52 F5.1 deg GLON Galactic longitude, System II.
55-59 F5.1 deg GLAT Galactic latitude, System II.
61-63 A3 --- ErrClas2 *Position & flux error class (character form)
65-72 A8 --- com *Remarks
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Note on 4C:
The 4C number. The first byte contains the zone sign; the first two
digits give the zone, while the last two sequentially number the
source in the zone (there are no sequential numbers over 100). Bytes
7-8 contain the characters ".1" only for source 4C+25.56.1, which was
added by Pilkington and Scott (1965MmRAS..69..183P 1965MmRAS..69..183P) after publication
of the catalog.
Note on RAh, RAm, RAs:
The positions were determined from interference pattern phases (see
Pilkington and Scott 1965MmRAS..69..183P 1965MmRAS..69..183P).
Note on FluxDen:
See source references for additional information. Byte 40 is blank for
sources having lower accuracy data.
Note on ErrClas1:
Numerical code for position and flux density error class. The codes
having e's and l's plus *'s are assigned the same numerical codes as
those without the asterisks (i.e. be* = be = 21). The codes are as
follows:
1 = a 11 = ae 14 = blank
2 = b 21 = be 15 = [1]
3 = c 31 = ce
13 = a* 12 = al
23 = b* 22 = bl
33 = c* 32 = cl
[1] a special code indicating that a character class is listed in
the published catalog, but the flux density is from 3C only and is
enclosed in parentheses.
Note on ErrClas2:
Position and flux density error class in character form (lower case
letters) corresponding to numerical code in bytes 43-44. The symbols
have the following meanings:
a,b,c: Error class of source; estimated standard errors for sources
in various ranges of flux density are given in Tables II and
III of the respective source references.
e: Possible right ascension lobe-shift earlier.
The magnitude of the lobe shift for each 1 degree interval is
given in Tables I of the source references.
l: Possible right ascension lobe-shift later.
*: The source is confused by a weaker uncatalogued one. The
weaker source will usually lie within 30' and have a flux
density at least 1/3 of the main source. The quoted error
class for each source includes the effect of such
confusing sources.
Note on com:
Remarks. Only cross identifications to the Revised 3C Catalogue
(Bennett 1962MmRAS..68..163B 1962MmRAS..68..163B) are actually given in the remarks field;
however, additional remarks given in the published catalog, for which
there is insufficient room in the 8-byte field, are indicated by an
asterisk. Asterisks can occur alone or with 3C numbers.
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Remarks and Modifications:
The machine-readable version of the 4C catalog was received on
magnetic tape from Dr. G. G. Pooley of Mullard Radio Astronomy
Observatory, Cambridge on 1 March 1983. As received, the file
consisted of 80-byte card images with a blank record following every
fifth data record. The following modifications were made so that the
data structures conform more closely to those of other computerized
catalogs and so that the data are easier to process and to interpret.
1. Blank records, clearly a problem for data processing, searching and
sorting, were removed.
2. The 4C numbers in the machine file were written as positive and
negative integers (e.g. 7901, -105, -7) rather than as real numbers
in the form ±xx.xx, as they are normally written in the literature.
The integers were converted to the present form.
3. Negative declinations had minus signs on both degrees and minutes.
The latter were removed, while minus signs were moved to all occur
in byte 23 and plus signs were added for positive declinations
(previously blank). Signs were also moved or added to byte 55 in the
Galactic latitude field. Preceding zeros were added to these fields
to make uniform numbers.
4. The file was sorted by 4C number to correspond exactly with the
published catalog. The error classes (in character form) and
remarks were keyed to a separate data set on disk. After interval
checks throughout the then 4843 records, the newly keyed records
were added to the original data set. The numerical and character
coded classes should be equivalent in all cases. The file was then
resorted by 4C number, South to North.
5. There were only 3623 sources in the printed 1967 catalog, while
3624 records are contained in the machine version. Source 4C+48.61,
found in the machine catalog, is missing from the published version.
The character class for 4C+48.61(a) was obtained from the machine
version and inserted. The source 4C+25.56.1, added as an addendum
to the 1965 publication, was in the machine version as a duplicate
of 4C+25.56. The ".1" was added to the 4C number (bytes 7-8) for
this record.
6. The logical record length was changed from 80 bytes to 72 bytes,
since bytes 72-80 were never used.
7. Numerical codes for 4C-02.07, 4C+21.19 and 4C+29.58 did not agree
with the published catalog, so they were corrected in the machine
version. The character and numerical codes have not been checked
entirely, so additional disagreements may be found. In these cases,
reference should be made to the source papers.
8. Some sources having numerical class code 14 were found to have
non-blank character codes in the published catalog. These sources
have only 3C flux densities enclosed in parentheses. To distinguish
them from published sources with blank class codes, a new numerical
code of 15 was defined and added to the appropriate records.
Acknowledgements:
The original ADC documentation by Wayne H. Warren, Jr. (1983) was used
to create this ReadMe file.
History:
* 27-Aug-2001: Declination of 4C+16.12 corrected, thanks to E. Davoust
* 03-Sep-2001: 3C counterpart of 4C+02.41 changed to 3C327 (ibid)
* 21-Aug-2025: Galactic cooordinates corredted for 4C+16.12,
thank to H. Andernach
References:
Bennett, A. S. 1962, Mem. Roy. Astron. Soc. 68, 163 (1962MmRAS..68..163B 1962MmRAS..68..163B)
Gower, J. F. R., Scott, P. F. and Wills D. 1967, Mem. Roy. Astron. Soc.
71, 49. (1967MmRAS..71...49G 1967MmRAS..71...49G)
Pilkington, J. D. H. and Scott, P. F. 1965, Mem. Roy. Astron. Soc. 69, 183.
(1965MmRAS..69..183P 1965MmRAS..69..183P)
(End) C.-H. Joseph Lyu [Hughes STX/NASA] 02-Apr-1996