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1959MmRAS...68...37Edge
Mem. RAS., 68, 37-60, 1959.

A Survey of radio sources at frequency 159 Mc/s.

Edge D.O., Shakeshaft J.R., McAdam W.B., Baldwin J.E., Archer S.
Summary The Cambridge four-element interferometer ahs been used at a frequency of 159 Mc/s to determine positions and flux densities for 471 radio sources lying between declinations -22^o and +71^o. Information concerning the angular diameters of some of the brighter sources has been obtained and the majority of these have diameters less than 6'. Most sources have a isotropic distribution but there is a concentration of the intense ones towards the galactic plane. There is also evidence for an excess in sources in the region of the belt of background radiation crossing the galactic plane at l=0d. If the number-flux density distribution is compared with that expected from a uniform distribution of sources in space, a dificit of the more intense sources is found.

History

The 1C catalog listed about 50 radio sources, detected at 3.7 m with a fixed meridian interferometer. (Later most of the sources from 1C were recognized to be the effect of confusion, i.e. they were not real objects.

Ryle M., Smith F.G., Elsmore B. A Preliminary Survey of the Radio Stars in the Northern Hemisphere, MNRAS, 110, 508-523 (1950).

The 2C catalog listed 1936 objects, observed at 3.7 m with an interferometer consisting of four equal antennas, placed in the corners of rectangle. The beam size was 2^o x 15^o.

Shakeshaft J.R. Ryle M., Baldwin J.E., Elsmore B., Thomson J.H. A Survey of the Radio sources Between Declinations -38^o and +83^o, Mem. Roy. Astron. Soc. 67, 106-154 (1955).

The 2C catalog was superseded with the 3C catalog, obtained at 159 MHz with the same instruments as the one used for 2C. The use of three different observation methods resulted in three parts of the survey.

3C(a) was derived from a system sensitive to sources with diameter <7' ( -10 < DEC < 55 ), the beam size (RA x dec) was 1.2 x 7.7^o.

3C(b) was obtained with a system sensitive to responses from sources with diameter < 1^o, and allowed to measure sizes from 2 to 10' ( -25 < DEC < 60 ), in 3C(c) contains sources with small sizes in the strip 52 < DEC < 70 ), The 3C catalog was limited by effects of confusion rather than by noise, and 471 sources > 8 Jy at 159 MHz were registered. Only 75 sources from the 2C catalog were confirmed in the 3C catalog.

It is included in the MASTER SOURCE LIST (MSL, Dixon, 1970).
3C sources have number 3C NNN.

If a 3CR source is absent in 3C list after source with number NNN (but before NNN+1) than it receives name 3C NNN.1; if these sources are two or three than they will be 3C NNN.2, 3C NNN.3 and so on. The same sources in 3C and 3CR have same name 3C NNN.0, while the 3C-source, not included in 3CR catalog, has name without point, for ex: 3C 193 ;