Deep Lens Survey
Encyclopedia
| February 26, 2001 | |
| February 14, 2002 | |
| March 5, 2000 | |
| February 23, 2001 | |
| March 26, 2001 | |
| April 3, 2003 |
The Deep Lens Survey (DLS, short for "Deep Gravitational Lensing Survey") is an ultra-deep multi-band
Spectroscopy
Spectroscopy is the study of the interaction between matter and radiated energy. Historically, spectroscopy originated through the study of visible light dispersed according to its wavelength, e.g., by a prism. Later the concept was expanded greatly to comprise any interaction with radiative...
optical survey of seven 4 square degree
Degree (angle)
A degree , usually denoted by ° , is a measurement of plane angle, representing 1⁄360 of a full rotation; one degree is equivalent to π/180 radians...
fields. Mosaic CCD
Charge-coupled device
A charge-coupled device is a device for the movement of electrical charge, usually from within the device to an area where the charge can be manipulated, for example conversion into a digital value. This is achieved by "shifting" the signals between stages within the device one at a time...
imagers at the National Optical Astronomy Observatory
National Optical Astronomy Observatory
The National Optical Astronomy Observatory is the United States national observatory for ground based nighttime ultraviolet-optical-infrared astronomy. The National Science Foundation funds NOAO to provide forefront astronomical research facilities for US astronomers...
's Blanco
Victor M. Blanco Telescope
The Víctor M. Blanco Telescope, also known as the Blanco 4m, is a 4m telescope located at the Cerro Tololo Inter-American Observatory, Chile. Commissioned in 1974 and completed in 1976, this telescope is similar to the Mayall 4m telescope located on Kitt Peak. In 1995 it was dedicated and named in...
(Cerro Tololo
Cerro Tololo Inter-American Observatory
The Cerro Tololo Inter-American Observatory is a complex of astronomical telescopes and instruments located at 30.169 S, 70.804 W, approximately 80 km to the East of La Serena, Chile at an altitude of 2200 metres. The complex is part of the National Optical Astronomy Observatory along with Kitt...
) and Mayall telescope
Nicholas U. Mayall Telescope
The Nicholas U. Mayall Telescope is a four meter reflector telescope located at the Kitt Peak National Observatory and named after Nicholas U. Mayall. It saw first light on February 27, 1973. Initial observers included: D. Crawford, Nicholas Mayall, and Arthur Hoag. It was dedicated on June 20,...
s (Kitt Peak
Kitt Peak National Observatory
The Kitt Peak National Observatory is a United States astronomical observatory located on 2,096 m Kitt Peak of the Quinlan Mountains in the Arizona-Sonoran Desert on the Tohono O'odham Nation, southwest of Tucson...
) are being used. The deep fields took five years to complete (2001–2006), in four bands: B, V
UBV photometric system
UBV photometric system, also called the Johnson system , is a wide band photometric system for classifying stars according to their colors. It is the first known standardized photoelectric photometric system. The letters U, B, and V stand for ultraviolet, blue, and visual magnitudes, which are...
, R, and z', to 29/29/29/28 mag
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...
per square arcsecond surface brightness. Optical transient events (including moving objects such as minor planet
Minor planet
An asteroid group or minor-planet group is a population of minor planets that have a share broadly similar orbits. Members are generally unrelated to each other, unlike in an asteroid family, which often results from the break-up of a single asteroid...
s and comet
Comet
A comet is an icy small Solar System body that, when close enough to the Sun, displays a visible coma and sometimes also a tail. These phenomena are both due to the effects of solar radiation and the solar wind upon the nucleus of the comet...
s) and supernova
Supernova
A supernova is a stellar explosion that is more energetic than a nova. It is pronounced with the plural supernovae or supernovas. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months...
candidates are released in real time.
The main goal of the survey is to produce unbiased maps of the large-scale structure of the mass distribution beyond the local universe, via very deep multicolor imaging of seven 2-degree fields and colour-redshift
Redshift
In physics , redshift happens when light seen coming from an object is proportionally increased in wavelength, or shifted to the red end of the spectrum...
s. The shear of distant galaxies
Galaxy
A galaxy is a massive, gravitationally bound system that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed dark matter. The word galaxy is derived from the Greek galaxias , literally "milky", a...
induced by the mass
Mass
Mass can be defined as a quantitive measure of the resistance an object has to change in its velocity.In physics, mass commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:...
of foreground structures will be measured. These weak-lensing
Weak gravitational lensing
While the presence of any mass bends the path of light passing near it, this effect rarely produces the giant arcs and multiple images associated with strong gravitational lensing. Most lines of sight in the universe are thoroughly in the weak lensing regime, in which the deflection is impossible...
observations are sensitive to all forms of clumped mass and will yield unbiased mass maps with resolution
Optical resolution
Optical resolution describes the ability of an imaging system to resolve detail in the object that is being imaged.An imaging system may have many individual components including a lens and recording and display components...
of one arcmin in the plane of the sky (about 120 kpc/h
Dimensionless Hubble parameter
Instead of working with the Hubble parameter, a common practice is to introduce the dimensionless Hubble parameter, usually noted h, and to write the Hubble's parameter H0 as being...
at z = 0.2
Redshift
In physics , redshift happens when light seen coming from an object is proportionally increased in wavelength, or shifted to the red end of the spectrum...
), in multiple redshift ranges. These maps will measure for the first time the change in large scale structure from z = 1 to the present epoch, and test the current theories of structure formation, which predict that mass in the low-redshift universe has a particular filamentary/sheetlike structure. These observations will directly constrain the clustering properties of matter, and, when compared with the results from microwave background anisotropy
Anisotropy
Anisotropy is the property of being directionally dependent, as opposed to isotropy, which implies identical properties in all directions. It can be defined as a difference, when measured along different axes, in a material's physical or mechanical properties An example of anisotropy is the light...
missions, will test the basic theory of structure formation via gravitational instability.
While this is the main goal of the survey, a wide-field imaging survey has a myriad of other uses. In addition, the group is acquiring the data in a way which makes it possible to detect variable objects on scales of hours to months, by spreading observations of individual subfields over 4 runs over two years.