The Third Cambridge Catalogue of Radio Sources (3C) is an

astronomical catalogue An astronomical catalogue is a list or tabulation of astronomical objects, typically grouped together because they share a common type, Galaxy morphological classification, morphology, origin, means of detection, or method of discovery. The olde ...

of celestial radio sources detected originally at 159 MHz, and subsequently at 178 MHz.

History

3C

The catalogue was published in 1959 by members of the Radio Astronomy Group of the

University of Cambridge The University of Cambridge is a Public university, public collegiate university, collegiate research university in Cambridge, England. Founded in 1209, the University of Cambridge is the List of oldest universities in continuous operation, wo ...

. Entries in the catalogue are identified by the prefix "3C" followed by the entry number, with a space - for example,

3C 273 3C 273 is a quasar located at the center of a giant elliptical galaxy in the constellation of Virgo. It was the first quasar ever to be identified and is the visually brightest quasar in the sky as seen from Earth, with an apparent visual magnitud ...

. The number denotes objects in order of increasing

right ascension Right ascension (abbreviated RA; symbol ) is the angular distance of a particular point measured eastward along the celestial equator from the Sun at the equinox (celestial coordinates), March equinox to the (hour circle of the) point in questio ...

. The catalogue was produced using the

Cambridge Interferometer The Cambridge Interferometer was a radio telescope interferometer built by Martin Ryle and Antony Hewish in the early 1950s to the west of Cambridge (between the Grange Road football ground and the current Cavendish Laboratory). The interferometer ...

on the west side of

Cambridge Cambridge ( ) is a List of cities in the United Kingdom, city and non-metropolitan district in the county of Cambridgeshire, England. It is the county town of Cambridgeshire and is located on the River Cam, north of London. As of the 2021 Unit ...

. The interferometer had previously been used for the

Second Cambridge Catalogue of Radio Sources The Second Cambridge Catalogue of Radio Sources (2C) was published in 1955 by John R Shakeshaft and colleagues. It comprised a list of 1936 sources between declinations -38 and +83, giving their right ascension, declination, both in 1950.0 coordina ...

(2C) survey, published in 1955.

3CR

The catalogue was subsequently revised by Bennett in 1962 using observations at 178 MHz, and for many years '3CR' was considered as the definitive listing of the brighter radio sources in the Northern Hemisphere. The revision resulted in a number of sources being deleted from the catalogue (as being below the flux limit of 9 Jy or as now-resolved blends of adjacent sources) and others being added. To avoid renumbering the existing sources (which were listed in RA order) these new sources were added using a decimal extension. E.g. 3C 323.1 follows 3C 323 in

Right Ascension Right ascension (abbreviated RA; symbol ) is the angular distance of a particular point measured eastward along the celestial equator from the Sun at the equinox (celestial coordinates), March equinox to the (hour circle of the) point in questio ...

and precedes

3C 324 3C may refer to: In astronomy: * 3C, the ''Third Cambridge Catalogue of Radio Sources'', an astronomical reference series In business: * 3C Records * 3C (radio), a defunct digital radio station * 3C (trade association), an American trade associ ...

3CRR

A further revision by R.A. Laing,

Julia Riley Julia M. Riley (née Hill, born 1947) is a British astrophysicist who developed the Fanaroff–Riley classification. Personal and professional background She is the daughter of Philippa (born Pass) and British marine geophysicist Maurice Hi ...

and

Malcolm Longair Malcolm Sim Longair (born 18 May 1941)Anon (2017) is a British physicist. From 1991 to 2008 he was the Jacksonian Professor of Natural Philosophy in the Cavendish Laboratory at the University of Cambridge. Since 2016 he has been Editor-in-Ch ...

in 1983, called 3CRR or 3CR², included galaxies which were not detected in the original catalogue due to shortcomings of the original observations, but which otherwise meet the flux and declination limits. This revision includes all extragalactic radio sources in the Northern Hemisphere with 178-MHz flux density greater that 10.9

Janskys The jansky (symbol Jy, plural ''janskys'') is a non-SI unit of spectral flux density, or spectral irradiance, used especially in radio astronomy. It is equivalent to 10−26 watts per square metre per hertz. The ''spectral flux density'' or ...

, declination greater than 10 degrees, and Galactic latitude greater than 10 degrees or less than -10 degrees. It excludes a number of well-known 3C/3CR objects, including all the supernova remnants from 3C, but also some well-known radio galaxies that lie outside the declination, flux density or galactic latitude constraints. Objects that had been discovered to consist of multiple components associated with different objects were given an alphabetical suffix (A, B...) to make it clear which component was part of the sample: e.g. the radio galaxy

3C 66B 3C 66B is an elliptical radio galaxy located in the constellation Andromeda. With an estimated redshift of 0.021258, the galaxy is about away. It has an angular separation of from the blazar 3C 66A, but the two are most likely unrelated. 3C 6 ...

is part of the sample, but the

BL Lac object A BL Lacertae object or BL Lac object is a type of active galactic nucleus (AGN) or a galaxy with such an AGN, named after its prototype, BL Lacertae. In contrast to other types of active galactic nuclei, BL Lacs are characterized by rapid and l ...

3C 66A 3C 66A is a blazar located in the constellation Andromeda. The "distance" of a far away galaxy depends on the distance measurement used. With a redshift of 0.444, light from this active galaxy is estimated to have taken around 4.5 billion year ...

is not.

References

* * *

External links

The Revised 3C Catalogue of Radio Sources
on the internet.
The 3CRR catalogue on the internet.
{{Radio surveys 3 *