astronomy Astronomy () is a natural science that studies astronomical object, celestial objects and phenomena. It uses mathematics, physics, and chemistry in order to explain their origin and chronology of the Universe, evolution. Objects of interest ...

, the 2dF Galaxy Redshift Survey (Two-degree-Field Galaxy Redshift Survey), 2dF or 2dFGRS is a

redshift survey 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 us ...

conducted by the Australian Astronomical Observatory (AAO) with the 3.9m

Anglo-Australian Telescope The Anglo-Australian Telescope (AAT) is a 3.9-metre equatorially mounted telescope operated by the Australian Astronomical Observatory and situated at the Siding Spring Observatory, Australia, at an altitude of a little over 1,100 m. In 20 ...

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 (

redshift In physics, a redshift is an increase in the wavelength, and corresponding decrease in the frequency and photon energy, of electromagnetic radiation (such as light). The opposite change, a decrease in wavelength and simultaneous increase in f ...

~ 0.2). It was the world's largest redshift survey between 1998 (overtaking Las Campanas Redshift Survey) and 2003 (overtaken by the Sloan Digital Sky Survey). Matthew Colless, Richard Ellis, Steve Maddox and John Peacock were in charge of the project. Team members

Shaun Cole Shaun Malcolm Cole (born 19 November 1963) is a British cosmologist and academic. He has been Professor of Physics at Durham University since 2005 and is the current director of the Institute for Computational Cosmology. He was joint-winner of ...

and John Peacock were awarded a share of the 2014

Shaw Prize The Shaw Prize is an annual award presented by the Shaw Prize Foundation. Established in 2002 in Hong Kong, it honours "individuals who are currently active in their respective fields and who have recently achieved distinguished and signifi ...

in astronomy for results from the 2dFGRS.

Description

The 2dF survey covered an area of about 1500

square degree __NOTOC__ A square degree (deg2) is a non- SI unit measure of solid angle. Other denotations include ''sq. deg.'' and (°)2. Just as degrees are used to measure parts of a circle, square degrees are used to measure parts of a sphere. Analogous to ...

s, surveying regions in both the north and the south galactic poles.2dFGRS − An Introduction
The name derives from the fact that the survey instrument has a 2 degree diameter field of view. The areas selected for observation were previously surveyed by the massive APM Galaxy Survey (on which Steve Maddox also worked). The regions surveyed cover roughly 75 degrees of

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 pai ...

for both bands, and the

declination In astronomy, declination (abbreviated dec; symbol ''δ'') is one of the two angles that locate a point on the celestial sphere in the equatorial coordinate system, the other being hour angle. Declination's angle is measured north or south of t ...

of the North Polar band was about 7.5 degrees while the declination of the South Polar band was about 15 degrees. Hundreds of isolated two degree fields near the South Polar band were also surveyed (se
this illustration
where black circles represent survey fields, and the red grid represents the earlier APM survey). In total, the photometry of 382,323 objects were measured, which includes spectra for 245,591 objects, of which 232,155 were

galaxies A galaxy is a system of stars, stellar remnants, interstellar gas, dust, dark matter, bound together by gravity. The word is derived from the Greek ' (), literally 'milky', a reference to the Milky Way galaxy that contains the Solar System. ...

(221,414 with good quality spectra), 12,311 are

star A star is an astronomical object comprising a luminous spheroid of plasma held together by its gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night, but their immense distances from Earth make ...

s, and 125 are quasi-stellar objects (quasars). The survey necessitated 272 required nights of observation, spread over 5 years. The survey was carried out with the 4 metre

, with the 2dF instrument installed at the primary focus permitting the observation of a field of 2 degrees per pointing. The instrument possesses a

spectrograph An optical spectrometer (spectrophotometer, spectrograph or spectroscope) is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify mat ...

equipped with two banks each of 200 optical fibres, permitting the simultaneous measurement of 400 spectra. The limiting apparent magnitude of the survey is 19.5, covering objects with a

mostly within less than z=0.3 and a median

of 0.11. The volume of the Universe covered by the survey is approximately 10⁸ ''h''⁻¹

Mpc MPC, Mpc or mpc may refer to: Astronomy * Megaparsec (Mpc), unit of length used in astronomy * Minor Planet Center, Smithsonian Astrophysical Observatory ** ''Minor Planet Circulars'' (MPC, M.P.C. or MPCs), astronomical publication from the Minor ...

³, where ''h'' corresponds to the value of the

Hubble constant Hubble's law, also known as the Hubble–Lemaître law, is the observation in physical cosmology that galaxies are moving away from Earth at speeds proportional to their distance. In other words, the farther they are, the faster they are moving ...

, ''H''₀, divided by 100. ''H''₀ is approximately 70 km/s/Mpc. The largest

observed by the survey corresponds to a distance of 600 ''h''⁻¹ Mpc.

Survey results

The principal results obtained for the field of

cosmology Cosmology () is a branch of physics and metaphysics dealing with the nature of the universe. The term ''cosmology'' was first used in English in 1656 in Thomas Blount's ''Glossographia'', and in 1731 taken up in Latin by German philosophe ...

by the 2dF survey are: * The measurement of the density parameter of non-relativistic matter (

baryonic matter In particle physics, a baryon is a type of composite subatomic particle which contains an odd number of valence quarks (at least 3). Baryons belong to the hadron family of particles; hadrons are composed of quarks. Baryons are also classifi ...

plus

dark matter Dark matter is a hypothetical form of matter thought to account for approximately 85% of the matter in the universe. Dark matter is called "dark" because it does not appear to interact with the electromagnetic field, which means it does not ab ...

plus massive

neutrinos A neutrino ( ; denoted by the Greek letter ) is a fermion (an elementary particle with spin of ) that interacts only via the weak interaction and gravity. The neutrino is so named because it is electrically neutral and because its rest mass ...

) * The detection of

Baryon acoustic oscillations In cosmology, baryon acoustic oscillations (BAO) are fluctuations in the density of the visible baryonic matter (normal matter) of the universe, caused by acoustic density waves in the primordial plasma of the early universe. In the same way ...

, and as a consequence the relationship between the density of baryonic matter and dark matter * Limits on the contribution of massive neutrinos to dark matter, putting a limit on the sum of the masses of the three families of neutrinos at 1.8 eV. All these results are in agreement with the measurements of other experiments, notably those of

WMAP The Wilkinson Microwave Anisotropy Probe (WMAP), originally known as the Microwave Anisotropy Probe (MAP and Explorer 80), was a NASA spacecraft operating from 2001 to 2010 which measured temperature differences across the sky in the cosmic mic ...

. They confirm the standard cosmological model. The 2dF survey also yields a unique view on our local cosmic environment. In the figure a 3-D reconstruction of the inner parts of the survey is shown, revealing an impressive view on the cosmic structures in the nearby universe. Several

superclusters A supercluster is a large group of smaller galaxy clusters or galaxy groups; they are among the largest known structures in the universe. The Milky Way is part of the Local Group galaxy group (which contains more than 54 galaxies), which in turn ...

stand out, such as the Sloan Great Wall, one of the largest structures in the universe known to date (see also Huge-LQG).

References

External links

Official site
of the 2dF Galaxy Redshift Survey
''The 2dF Galaxy Redshift Survey: spectra and redshifts''
− 2001

Royal Astronomical Society (Whatever shines should be observed) , predecessor = , successor = , formation = , founder = , extinction = , merger = , merged = , type = NG ...

paper describing the survey
Official site
of the Two Degree Field instrument system {{Portal bar, Astronomy, Stars, Spaceflight, Outer space, Solar System Observational astronomy Astronomical surveys 1997 in science

Description

Survey results

See also

References

External links