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The Ninth Cambridge (9C) Survey of Radio Sources

The 9C survey of radio sources was made with the Ryle Telescope at a frequency of 15.2 GHz and a resolution of 25 x 25 cosec(dec) arcsec2.

It was set up as part of the observing strategy of the Very Small Array (VSA) and its prime motivation was to define a catalogue of the foreground sources to be monitored by the VSA during its observations of the cosmic microwave background. It is, however, of much wider interest, being the first survey to cover an appreciable area at a comparable radio frequency.

The regions surveyed correspond to the fields chosen for the VSA observations, rather than forming one large contiguous area. Two data releases are now available:

9C Data Release 1

Waldram, E.M., Pooley, G.G., Grainge, K.J.B., Jones, M.E., Saunders, R.D.E., Scott, P.F., Taylor, A.C., 2003, MNRAS, 342, 915
comprises three circular regions covering a total area of 520 deg2 with a completeness limit of 25 mJy. Details of the regions are specified in the table below.

The corresponding source catalogues are described by an accompanying CDS-style ReadMe file. They can be accessed here – or you can use the individual links in the table below.

Field name RA, Dec of centre (J2000) Radius No. of sources
0020p30.dat 00h 17m 36.5s   30° 16′ 39″ 5.5° 84
0940p32.dat 09h 40m 57.7s   31° 46′ 21″ 6.0° 103
1540p43.dat 15h 36m 42.7s   43° 20′ 11″ 5.0° 55

These source lists are complete to ~ 25 mJy and at present no sources are included below that level.

Radio and optical follow-up

Radio and optical follow-up investigations have been carried out for 176 of the catalogued sources. For full details see:
Bolton, R.C., Cotter, G., Pooley, G.G., Riley, J.M., Waldram, E.M., Chandler, C.J., Mason, B.S., Pearson, T.J., Readhead, A.C.S., 2004, MNRAS, 354, 485
you can also access the NED plots of radio spectra published in this paper as gzipped postscript files .

9C Data Release 2

Waldram, E.M., Pooley, G.G., Davies, M.L., Grainge, K.J.B., Scott, P.F. 2010, MNRAS, 404, 1005

This is a deeper survey, driven as before by the source-monitoring requirements of the VSA observation programme.

It comprises seven fields, each delineated by boundaries in RA and Dec, together covering a total of 114.7 deg2 for which the source catalogue is complete to ~ 10 mJy. Within in each of these fields are a number of more sensitive areas – amounting to 29.1 deg2 in total – for which completeness to ~ 5.5 mJy is achieved. The accompanying 2-page document tabulates the RA and Dec specifications of the seven major fields and those of the more sensitive the sub-areas within them, and provides figures illustrating the layouts.

You can download the source list in ASCII format with an accompanying CDS-style ReadMe file. Alternatively, a pdf source list suitable for printing is also provided.

Last modified 19 May 2010

Guy Pooley (
Elizabeth Waldram (