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

astronomical catalogue An astronomical catalog or catalogue is a list or tabulation of astronomical objects, typically grouped together because they share a common type, morphology, origin, means of detection, or method of discovery. The oldest and largest are star cat ...

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 , mottoeng = Literal: From here, light and sacred draughts. Non literal: From this place, we gain enlightenment and precious knowledge. , established = , other_name = The Chancellor, Masters and Schola ...

. 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 in the constellation of Virgo (constellation), Virgo. It was the first quasar ever to be identified. It is the optically brightest quasar in the sky from Earth (apparent magnitude, m ~12.9), and one of the closest with ...

. The catalogue was produced using the

Cambridge Interferometer {{Infobox telescope 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) ...

on the west side of

Cambridge Cambridge ( ) is a university city and the county town in Cambridgeshire, England. It is located on the River Cam approximately north of London. As of the 2021 United Kingdom census, the population of Cambridge was 145,700. Cambridge bec ...

. 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 March equinox to the (hour circle of the) point in question above the earth. When paired w ...

and precedes

3C 324 3C may refer to: In astronomy: * 3C, the ''Third Cambridge Catalogue of Radio Sources'', an astronomical reference series In business: * Long March 3C, a 2008 Chinese orbital rocket * 3C Records, a record label * 3C (radio), a defunct digital rad ...

3CRR

A further revision by Laing,

Julia Riley Julia M. Riley (née Hill) 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 Hill and grand ...

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-c ...

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 ''flux density'' or ''mono ...

, 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 Fanaroff and Riley class 1 radio galaxy located in the constellation Andromeda. With an estimated redshift of 0.021258, the galaxy is about 300 million light-years away. The orbital motion of 3C 66B showed supposed e ...

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 ye ...

is not.

References

* * *

External links

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