8004 VIII/4 Fourth Cambridge Survey of Radio Sources J D H Pilkington P F Scott Mem. Roy. Astron. Soc. 69 183 1965 1965MmRAS..69..183P J F R Gower P F Scott D Wills Mem. Roy. Astron. Soc. 71 49 1967 1967MmRAS..71...49G Surveys Radio sources The Fourth Cambridge Radio Survey (4C) Catalogue contains all survey data from the papers of Pilkington and Scott (1965) and Gower, Scott and Wills (1967). 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.

ID The 4C number 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 (1965) after publication of the catalog. --- RAh Right ascension equinox 1950.0 The positions were determined from interference pattern phases (see Pilkington and Scott 1965). h RAm R.A. in minutes min RAs R.A. in seconds s DE- Sign of declination equinox 1950.0 --- DEd Dec. deg DEm Dec. arcmin FluxDen Flux density (1.0E-26 MKS) at 178 MHz See source references for additional information. Byte 40 is blank for sources having lower accuracy data. W/m2/Hz ErrClas1 Position and flux error class (in number) 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. --- GLON Galactic longitude, System II. deg GLAT Galactic latitude, System II. deg ErrClas2 Position & flux error class (character form) 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 uncataloged 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. --- com Remarks Remarks. Only cross identifications to the Revised 3C Catalogue (Bennett 1962) 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. --- C.-H. Joseph Lyu Hughes STX/NASA 1996Apr02The original ADC documentation by Wayne H. Warren, Jr. (1983) was used to create this ReadMe file. UNKNOWN UNKNOWN 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. VIII_4.xml