Editing Redshift (section)

===Redshift surveys===
{{Main|Redshift survey}}
[[File:2dfgrs.png|thumb|Rendering of the 2dFGRS data]]
With advent of automated [[telescope]]s and improvements in [[astronomical spectroscopy|spectroscopes]], a number of collaborations have been made to map the universe in redshift space. 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 properties of the [[Observable universe|large-scale structure]] of the universe. The [[CfA2 Great Wall|Great Wall]], a vast [[supercluster]] of galaxies over 500 million [[light-year]]s wide, provides a dramatic example of a large-scale structure that redshift surveys can detect.<ref>{{cite journal | title=Mapping the Universe | first1=M. J. | last1=Geller | first2=J. P. | last2=Huchra | journal=Science | volume=246 | issue=4932 | pages=897–903 | year=1989 | doi=10.1126/science.246.4932.897 | pmid=17812575 | bibcode=1989Sci...246..897G | s2cid=31328798 }}</ref>

The first redshift survey was the [[CfA Redshift Survey]], started in 1977 with the initial data collection completed in 1982.<ref>See the CfA website for more details: {{cite web
 | title=The CfA Redshift Survey
 | first=John P. | last=Huchra | author-link=John Huchra
 | publisher=Harvard & Smithsonian Center for Astrophysics
 | url=https://lweb.cfa.harvard.edu/~dfabricant/huchra/zcat/
 | access-date=2023-03-20
}}</ref> More recently, the [[2dF Galaxy Redshift Survey]] determined the large-scale structure of one section of the universe, measuring redshifts for over 220,000 galaxies; data collection was completed in 2002, and the final [[data set]] was released 30 June 2003.<ref>{{cite journal
 |title=The 2dF galaxy redshift survey: Power-spectrum analysis of the final dataset and cosmological implications
 | first1=Shaun | last1=Cole | author-link=Shaun Cole
 | last2=Percival | first2=Will J. | last3=Peacock | first3=John A.
 | last4=Norberg | first4=Peder | last5=Baugh | first5=Carlton M.
 | last6=Frenk | first6=Carlos S. | last7=Baldry | first7=Ivan
 | last8=Bland-Hawthorn | first8=Joss | last9=Bridges | first9=Terry
 | last10=Cannon | first10=Russell | last11=Colless | first11=Matthew
 | last12=Collins | first12=Chris | last13=Couch | first13=Warrick
 | last14=Cross | first14=Nicholas J. G. | last15=Dalton | first15=Gavin
 | last16=Eke | first16=Vincent R. | last17=De Propris | first17=Roberto
 | last18=Driver | first18=Simon P. | last19=Efstathiou | first19=George
 | last20=Ellis | first20=Richard S. | last21=Glazebrook | first21=Karl
 | last22=Jackson | first22=Carole | last23=Jenkins | first23=Adrian
 | last24=Lahav | first24=Ofer | last25=Lewis | first25=Ian
 | last26=Lumsden | first26=Stuart | last27=Maddox | first27=Steve
 | last28=Madgwick | first28=Darren | last29=Peterson | first29=Bruce A.
 | last30=Sutherland | first30=Will | last31=Taylor | first31=Keith
 | journal=Monthly Notices of the Royal Astronomical Society
 | volume=362 | issue=2 | pages=505–34 | date=2005
 | bibcode=2005MNRAS.362..505C | arxiv=astro-ph/0501174
 | doi=10.1111/j.1365-2966.2005.09318.x
 | doi-access=free | s2cid=6906627| display-authors=4
}} [http://msowww.anu.edu.au/2dFGRS/ 2dF Galaxy Redshift Survey homepage] {{Webarchive|url=https://web.archive.org/web/20070205010241/http://msowww.anu.edu.au/2dFGRS/ |date=2007-02-05 }}</ref> The [[Sloan Digital Sky Survey]] (SDSS) began collecting data in 1998<ref>{{cite journal |last1=Gunn |first1=James E. |last2=Siegmund |first2=Walter A. |last3=Mannery |first3=Edward J. |last4=Owen |first4=Russell E. |last5=Hull |first5=Charles L. |last6=Leger |first6=R. French |display-authors=etal |date=April 2006 |title=The 2.5 m Telescope of the Sloan Digital Sky Survey |journal=The Astronomical Journal |volume=131 |issue=4 |pages=2332–2359 |doi=10.1086/500975 |doi-access=free |arxiv=astro-ph/0602326 |bibcode=2006AJ....131.2332G }}</ref> and published its eighteenth data release in 2023.<ref>{{cite journal|last1=Almeida |first1=Andrés |display-authors=etal |title=The Eighteenth Data Release of the Sloan Digital Sky Surveys: Targeting and First Spectra from SDSS-V |journal=The Astrophysical Journal Supplement Series |date=2023 |volume=267 |number=2 |page=44 |doi=10.3847/1538-4365/acda98 |doi-access=free |arxiv=2301.07688 |bibcode=2023ApJS..267...44A}}</ref> SSDS has measured redshifts for galaxies as high as 0.8, and has recorded over 100,000 [[quasar]]s at {{math|''z'' {{=}} 3}} and beyond.<ref>{{cite web|url=https://www.sdss4.org/science/ |title=Science Results |website=SSDS |access-date=2025-05-20 }}</ref> The [[DEEP2 Redshift Survey]] used the [[Keck telescopes]] with the "DEIMOS" [[spectrograph]]; a follow-up to the pilot program DEEP1, DEEP2 was designed to measure faint galaxies with redshifts 0.7 and above, and it recorded redshifts of over 38,000 objects by its conclusion in 2013.<ref>{{cite conference | title=Science objectives and early results of the DEEP2 redshift survey| first1=Marc | last1=Davis |collaboration=DEEP2 collaboration |date=2002 | conference=Conference on Astronomical Telescopes and Instrumentation, Waikoloa, Hawaii, 22–28 Aug 2002 | arxiv=astro-ph/0209419 | bibcode=2003SPIE.4834..161D | doi=10.1117/12.457897 }}</ref><ref>{{cite journal|first1=Jeffrey A. |last1=Newman |display-authors=etal |title=The DEEP2 Galaxy Redshift Survey: Design, Observations, Data Reduction, and Redshifts |journal=The Astrophysical Journal Supplement Series |year=2013 |volume=208 |number=1 |page=5 |doi=10.1088/0067-0049/208/1/5|arxiv=1203.3192 |bibcode=2013ApJS..208....5N }}</ref>