redshift survey


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redshift survey

A three-dimensional mapping of galaxies in a large region of the sky, obtained by measuring the redshifts of all the galaxies down to a certain limiting magnitude. The redshifts allow distances to be determined using Hubble's law; the sky positions are known. Many redshift surveys have been undertaken using different strategies varying from automatic measurement of optical photographic plates (see APM; COSMOS) and pencil-beam surveys to galaxies selected by their infrared emission. Redshift surveys are important in tracing the large-scale structure of the Universe into its constituent superclusters, voids, and filaments. Major surveys include the Harvard–Smithsonian CfA (Center for Astrophysics) survey (see illustration), the Las Campanas redshift survey, the 2df survey , and the Sloan Digital Sky Survey.