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 near Cambridge. AMI was designed, built and is operated by the Cavendish Astrophysics Group. 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, vi ...
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 e ...
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 ...
, 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 element ...
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 on ...
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 creat ...
. 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 telescope, optical or radio telescope, a microscope, a camera, or an Human eye, eye, to distinguish small details of an object, thereby making it a major det ...
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 193 ...
(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 distributi ...
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
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 ma ...
s and anomalous microwave emission
In astronomy, spinning dust emission is a mechanism proposed to explain anomalous microwave emission from the Milky Way. The emission could arise from the electric dipole of very rapidly spinning (10–60 GHz) extremely small (nanometer) dus ...
.
See also
*South Pole Telescope
The South Pole Telescope (SPT) is a diameter telescope located at the Amundsen–Scott South Pole Station, Antarctica. The telescope is designed for observations in the microwave, millimeter-wave, and submillimeter-wave regions of the electroma ...
* Sunyaev-Zel'dovich Array
* Atacama Cosmology Telescope
The Atacama Cosmology Telescope (ACT) is a cosmological millimeter-wave telescope located on Cerro Toco in the Atacama Desert in the north of Chile. ACT makes high-sensitivity, arcminute resolution, microwave-wavelength surveys of the sky in or ...
References
* * * * * * * {{Authority control Cosmic microwave background experiments Cavendish Laboratory Interferometric telescopes Radio telescopes