astronomy Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest includ ...

, 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 astronomical surveys, 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 ...

conducted by the

Australian Astronomical Observatory The Australian Astronomical Observatory (AAO), formerly the Anglo-Australian Observatory, was an optical and near-infrared astronomy observatory with its headquarters in North Ryde in suburban Sydney, Australia. Originally funded jointly by the G ...

(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 (

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 increase in frequency and e ...

~ 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 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 began in 2000 a ...

). 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.

Description

The 2dF survey covered an area of about 1500 square degrees, 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 equinox (celestial coordinates), March equinox to the (hour circle of the) point in questio ...

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. The declination angle is measured north (positive) or ...

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 Photometry can refer to: * Photometry (optics), the science of measurement of visible light in terms of its perceived brightness to human vision * Photometry (astronomy), the measurement of the flux or intensity of an astronomical object's electr ...

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, and 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 Sys ...

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

star A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...

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 Anglo-Australian Telescope, 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 mate ...

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 Mpc³, 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 a galaxy is from the Earth, the faste ...

, ''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 cosmos. The term ''cosmology'' was first used in English in 1656 in Thomas Blount's ''Glossographia'', with the meaning of "a speaking of the wo ...

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 that contains an odd number of valence quarks, conventionally three. Protons and neutrons are examples of baryons; because baryons are composed of quarks, they belong to ...

plus

dark matter In astronomy, dark matter is an invisible and hypothetical form of matter that does not interact with light or other electromagnetic radiation. Dark matter is implied by gravity, gravitational effects that cannot be explained by general relat ...

plus massive

neutrinos A neutrino ( ; denoted by the Greek letter ) is an elementary particle that interacts via the weak interaction and gravity. The neutrino is so named because it is electrically neutral and because its rest mass is so small ('' -ino'') that it ...

) * The detection of Baryon acoustic oscillations, 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. 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 a view on the cosmic structures in the nearby universe. Several superclusters 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 The Royal Astronomical Society (RAS) is a learned society and charitable organisation, charity that encourages and promotes the study of astronomy, planetary science, solar-system science, geophysics and closely related branches of science. Its ...

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

Description

Survey results

See also

References

External links