Surveys
Of the five surveys in UKIDSS, two are directed towards Galactic targets and three are optimized for extra-Galactic observations. The surveys are described here in decreasing order of area. The letters refer to spectral regions; e.g. JHK is a combination of near-infrared filters, more or less synonymous with "the near-infrared".
Large Area Survey (LAS)
The LAS (extra-Galactic) covers an area of 4000 square degrees in YJHK to a depth of K = 18.4. This area has previously been covered at optical wavelengths in the Sloan Digital Sky Survey. While the high Galactic latitudes covered by the LAS make it suitable for observations of sources outside the Milky Way, the survey also targets Galactic sources, incorporating a second pass in J to measure proper motions of nearby stars.
Galactic Plane Survey (GPS)
The GPS (Galactic) covers an area of 1800 square degrees in JHK to a depth of K=19.0, with 300 square degrees also covered through a narrow-band H2 filter. The motivation for the GPS is to obtain a clearer view of the Galactic Plane than is possible at optical wavelengths, due to absorption by material in the disk of the galaxy.
Galactic Clusters Survey (GCS)
The GCS (Galactic) covers an area of 1400 square degrees in JHK to a depth of K=18.7. The area is distributed over ten open star clusters with the aim of measuring the mass function in a variety of Galactic environments.
The DXS (extra-Galactic) covers an area of 35 square degrees in JK to a depth of K=21.0 with 5 square degrees also imaged in H. The survey fields are at high Galactic latitudes with low extinction, and are chosen to overlap with deep observations made at other wavelengths.
Ultra Deep Survey (UDS)
The UDS (extra-Galactic) covers an area of 0.77 square degrees within the XMM-LSS field (which is contained within the DXS) in JHK to a depth of K=23.0. This is the deepest near-infrared survey yet conducted over such an area of sky, with the aim of studying the formation and evolution of galaxies in the early Universe.
The United Kingdom Infra-Red Telescope (UKIRT) is a 3.8 metre (150 inch) infrared reflecting telescope, the second largest dedicated infrared telescope in the world. It is located on Mauna Kea, Hawai'i as part of Mauna Kea Observatory. Until 2014 it was operated by the Joint Astronomy Centre in Hilo. It was owned by the United Kingdom Science and Technology Facilities Council. UKIRT is currently being funded by NASA and operated under scientific cooperation between Lockheed Martin Advanced Technology Center, the University of Hawaii, and the U. S. Naval Observatory. The telescope is set to be decommissioned after completion of the Thirty Meter Telescope as part of the Mauna Kea Comprehensive Management Plan.
Photometry, from Greek photo- ("light") and -metry ("measure"), is a technique used in astronomy that is concerned with measuring the flux or intensity of light radiated by astronomical objects. This light is measured through a telescope using a photometer, often made using electronic devices such as a CCD photometer or a photoelectric photometer that converts light into an electric current by the photoelectric effect. When calibrated against standard stars of known intensity and colour, photometers can measure the brightness or apparent magnitude of celestial objects.
The Hubble Deep Field (HDF) is an image of a small region in the constellation Ursa Major, constructed from a series of observations by the Hubble Space Telescope. It covers an area about 2.6 arcminutes on a side, about one 24-millionth of the whole sky, which is equivalent in angular size to a tennis ball at a distance of 100 metres. The image was assembled from 342 separate exposures taken with the Space Telescope's Wide Field and Planetary Camera 2 over ten consecutive days between December 18 and 28, 1995.
The Hubble Ultra-Deep Field (HUDF) is an image of a small region of space in the constellation Fornax, containing an estimated 10,000 galaxies. The original release was combined from Hubble Space Telescope data accumulated over a period from September 24, 2003, through to January 16, 2004. Looking back approximately 13 billion years, it has been used to search for galaxies that existed at that time. The HUDF image was taken in a section of the sky with a low density of bright stars in the near-field, allowing much better viewing of dimmer, more distant objects. In August and September 2009, the HUDF field was observed at longer wavelengths using the infrared channel of the recently attached Wide Field Camera 3 (WFC3) instrument. When combined with existing HUDF data, astronomers were able to identify a new list of potentially very distant galaxies.
The Sloan Digital Sky Survey or SDSS is a major multi-spectral imaging and spectroscopic redshift survey using a dedicated 2.5-m wide-angle optical telescope at Apache Point Observatory in New Mexico, United States. The project was named after the Alfred P. Sloan Foundation, which contributed significant funding.
In astronomy, a redshift survey is a survey of a section of the sky to measure the redshift of astronomical objects: usually galaxies, but sometimes other objects such as galaxy clusters or quasars. Using Hubble's law, the redshift can be used to estimate the distance of an object from Earth. By combining redshift with angular position data, a redshift survey maps the 3D distribution of matter within a field of the sky. These observations are used to measure detailed statistical properties of the large-scale structure of the universe. In conjunction with observations of early structure in the cosmic microwave background, these results can place strong constraints on cosmological parameters such as the average matter density and the Hubble constant.
In astronomy, the 2dF Galaxy Redshift Survey, 2dF or 2dFGRS is a redshift survey conducted by the Australian Astronomical Observatory (AAO) with the 3.9m Anglo-Australian Telescope between 1997 and 11 April 2002. The data from this survey were made public on 30 June 2003. The survey determined the large-scale structure in two large slices of the Universe to a depth of around 2.5 billion light years. It was the world's largest redshift survey between 1998 and 2003. Matthew Colless, Richard Ellis, Steve Maddox and John Peacock were in charge of the project. Team members Shaun Cole and John Peacock were awarded a share of the 2014 Shaw Prize in astronomy for results from the 2dFGRS.
An astronomical survey is a general map or image of a region of the sky that lacks a specific observational target. Alternatively, an astronomical survey may comprise a set of many images or spectra of objects that share a common type or feature. Surveys are often restricted to one band of the electromagnetic spectrum due to instrumental limitations, although multiwavelength surveys can be made by using multiple detectors, each sensitive to a different bandwidth.
The Hubble Deep Field South is a composite of several hundred individual images taken using the Hubble Space Telescope's Wide Field and Planetary Camera 2 over 10 days in September and October 1998. It followed the great success of the original Hubble Deep Field in facilitating the study of extremely distant galaxies in early stages of their evolution. While the WFPC2 took very deep optical images, nearby fields were simultaneously imaged by the Space Telescope Imaging Spectrograph (STIS) and the Near Infrared Camera and Multi-Object Spectrometer (NICMOS).
SkyMapper is a fully automated 1.35 m (4.4 ft) wide-angle optical telescope at Siding Spring Observatory in northern New South Wales, Australia. It is one of the telescopes of the Research School of Astronomy and Astrophysics of the Australian National University (ANU). The telescope has a compact modified Cassegrain design with a large 0.69 m secondary mirror, which gives it a very wide field of view: its single, dedicated instrument, a 268-million pixel imaging camera, can photograph 5.7 square degrees of sky. The camera has six light filters which span from ultraviolet to near infrared wavelengths.
The Wide Field Infrared Explorer (WIRE) was a satellite launched on 5 March 1999, on the Pegasus XL rocket into polar orbit between 409 and 426 km above the Earth's surface. WIRE was intended to be a four-month infrared survey of the entire sky at 21-27 µm and 9-15 µm, specifically focusing on starburst galaxies and luminous protogalaxies.
A photometric redshift is an estimate for the recession velocity of an astronomical object such as a galaxy or quasar, made without measuring its spectrum. The technique uses photometry to determine the redshift, and hence, through Hubble's law, the distance, of the observed object.
In astronomy, color–color diagrams are a means of comparing the apparent magnitudes of stars at different wavelengths. Astronomers typically observe at narrow bands around certain wavelengths, and objects observed will have different brightnesses in each band. The difference in brightness between two bands is referred to as color. On color–color diagrams, the color defined by two wavelength bands is plotted on the horizontal axis, and then the color defined by another brightness difference will be plotted on the vertical axis.
Cosmic infrared background is infrared radiation caused by stellar dust.
The Great Observatories Origins Deep Survey, or GOODS, is an astronomical survey combining deep observations from three of NASA's Great Observatories: the Hubble Space Telescope, the Spitzer Space Telescope, and the Chandra X-ray Observatory, along with data from other space-based telescopes, such as XMM Newton, and some of the world's most powerful ground-based telescopes.
The 6dF Galaxy Survey, 6dF or 6dFGS is a redshift survey conducted by the Anglo-Australian Observatory (AAO) with the 1.2m UK Schmidt Telescope between 2001 and 2009. The data from this survey were made public on 31 March, 2009. The survey has mapped the nearby universe over nearly half the sky. Its 136,304 spectra have yielded 110,256 new extragalactic redshifts and a new catalog of 125,071 galaxies. For a subsample of 6dF a peculiar velocity survey is measuring mass distribution and bulk motions of the local Universe. As of July 2009, it is the third largest redshift survey next to the Sloan Digital Sky Survey (SDSS) and the 2dF Galaxy Redshift Survey (2dFGRS).
A Pea galaxy, also referred to as a Pea or Green Pea, might be a type of luminous blue compact galaxy that is undergoing very high rates of star formation. Pea galaxies are so-named because of their small size and greenish appearance in the images taken by the Sloan Digital Sky Survey (SDSS).
Euclid is a visible to near-infrared space telescope currently under development by the European Space Agency (ESA) and the Euclid Consortium. The objective of the Euclid mission is to better understand dark energy and dark matter by accurately measuring the acceleration of the universe. To achieve this, the Korsch-type telescope will measure the shapes of galaxies at varying distances from Earth and investigate the relationship between distance and redshift. Dark energy is generally accepted as contributing to the increased acceleration of the expanding universe, so understanding this relationship will help to refine how physicists and astrophysicists understand it. Euclid's mission advances and complements ESA's Planck telescope. The mission is named after the ancient Greek mathematician Euclid of Alexandria.
The Lockman Hole is an area of the sky in which minimal amounts of neutral hydrogen gas are observed. Clouds of neutral hydrogen glow faintly with infrared light and obscure distant views at extreme ultraviolet and soft x-ray wavelengths. They interfere with observations at those wavelengths in nearly all other directions since they are common in our galaxy. So the Lockman Hole serves as a relatively clear window on distant objects, which makes it an attractive area of the sky for observational astronomy surveys. It is located near the pointer stars of the Big Dipper in the constellation Ursa Major and is about 15 square degrees in size. It is named after its discoverer, astronomer Jay Lockman.
