The Arcminute Microkelvin Imager (AMI) consists of a pair of

interferometric Interferometry is a technique which uses the ''interference'' of superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important investigative technique in the fields of astronomy, fiber op ...

radio telescope A radio telescope is a specialized antenna and radio receiver used to detect radio waves from astronomical radio sources in the sky. Radio telescopes are the main observing instrument used in radio astronomy, which studies the radio frequency ...

s - the Small and Large Arrays - located at the

Mullard Radio Astronomy Observatory The Mullard Radio Astronomy Observatory (MRAO) is located near Cambridge, UK and is home to a number of the largest and most advanced aperture synthesis radio telescopes in the world, including the One-Mile Telescope, 5-km Ryle Telescope, and ...

near

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 ...

. AMI was designed, built and is operated by the

Cavendish Astrophysics Group The Cavendish Astrophysics Group (formerly the Radio Astronomy Group) is based at the Cavendish Laboratory at the University of Cambridge. The group operates all of the telescopes at the Mullard Radio Astronomy Observatory except for the 32m MERLI ...

. AMI was designed, primarily, for the study of

galaxy clusters A galaxy cluster, or a cluster of galaxies, is a structure that consists of anywhere from hundreds to thousands of galaxies that are bound together by gravity, with typical masses ranging from 1014 to 1015 solar masses. They are the second-la ...

by observing secondary

anisotropies Anisotropy () is the property of a material which allows it to change or assume different properties in different directions, as opposed to isotropy. It can be defined as a difference, when measured along different axes, in a material's physic ...

in the

cosmic microwave background In Big Bang cosmology the cosmic microwave background (CMB, CMBR) is electromagnetic radiation that is a remnant from an early stage of the universe, also known as "relic radiation". The CMB is faint cosmic background radiation filling all spac ...

(CMB) arising from the Sunyaev–Zel'dovich (SZ) effect. Both arrays are used to observe

radiation In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. This includes: * ''electromagnetic radiation'', such as radio waves, microwaves, infrared, visi ...

with

frequencies Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...

between 12 and 18

GHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that one he ...

, and have very similar system designs. The telescopes are used to observe both previously known galaxy clusters, in an attempt to determine, for example, their

mass Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different elementar ...

es and

temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied o ...

s, and to carry out surveys, in order to locate previously undiscovered clusters.

AMI Large Array

The AMI Large Array (AMI LA) is composed of eight 12.8-metre-diameter, equatorially mounted

parabolic antenna A parabolic antenna is an antenna that uses a parabolic reflector, a curved surface with the cross-sectional shape of a parabola, to direct the radio waves. The most common form is shaped like a dish and is popularly called a dish antenna or pa ...

s, which were previously part of the

Ryle Telescope {{Infobox telescope The Ryle Telescope (named after Martin Ryle, and formerly known as the 5-km Array) was a linear east-west radio telescope array at the Mullard Radio Astronomy Observatory. In 2004, three of the telescopes were moved to create ...

. The antennas are separated by distances ranging between 18 and 110 m. The telescope has an

angular resolution Angular resolution describes the ability of any image-forming device such as an optical or radio telescope, a microscope, a camera, or an eye, to distinguish small details of an object, thereby making it a major determinant of image resolution. ...

of approximately 30

arcseconds A minute of arc, arcminute (arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of one degree. Since one degree is of a turn (or complete rotation), one minute of arc is of a turn. The na ...

. The LA is used to image the

radio sources An astronomical radio source is an object in outer space that emits strong radio waves. Radio emission comes from a wide variety of sources. Such objects are among the most extreme and energetic physical processes in the universe. History In 1932 ...

(mainly

radio galaxies A radio galaxy is a galaxy with giant regions of radio emission extending well beyond its visible structure. These energetic radio lobes are powered by jets from its active galactic nucleus. They have luminosities up to 1039 W at radio wav ...

) that contaminate the Small Array observations of the CMB. The LA is being used to carry out the Tenth Cambridge Survey of radio sources. The first results from the survey were used to extend the measured 15-GHz

source counts The source counts distribution of radio-sources from a radio-astronomical survey is the cumulative distribution of the number of sources (''N'') brighter than a given flux density (''S''). As it is usually plotted on a log-log scale its distributio ...

to sub- millijansky levels; this is an order of magnitude deeper than achieved by the Ninth Cambridge Survey, which was the first survey of significant sky coverage at a comparable radio frequency.

AMI Small Array

Arcminute microkelvin imager small array

The AMI Small Array (AMI SA) consists of 10 3.7-m-diameter antennas, similar in design to those of the LA. They are arranged at intervals of between 5 and 20 m. The SA has an angular resolution of approximately 3 arcminutes and is used to image, at high resolution, the galaxy clusters of interest. The SA is being used to search for previously unknown galaxy clusters; results from the first such cluster, detected using AMI, were released in December 2010. In addition to observations of galaxy clusters, the SA has been used to carry out observations, amongst other things, towards

supernova remnant A supernova remnant (SNR) is the structure resulting from the explosion of a star in a supernova. The supernova remnant is bounded by an expanding shock wave, and consists of ejected material expanding from the explosion, and the interstellar mat ...

s and anomalous microwave emission.

References

* * * * * * * {{Authority control Cosmic microwave background experiments Cavendish Laboratory Interferometric telescopes Radio telescopes

AMI Large Array

AMI Small Array

See also

References