Survey captures local universe in 3-D

Most complete view yet of the nearby cosmos

The cosmic backyard will never look the same, thanks to a new three-dimensional map — the most detailed view ever assembled out to a distance of 380 million light-years.

Covering 95 percent of the sky, this new infrared map is the most detailed ever assembled of galaxies in the local universe. Purple dots denote the closest galaxies and red the farthest, lying about 1 billion light-years from Earth. Tom Jarrett/IPAC/Caltech and the 2MASS Redshift Survey team

Covering 95 percent of the sky, the map uses dust-penetrating infrared observations to reveal features that in visible light are obscured by the Milky Way. “We get a more detailed look at major structures that are almost hidden by our galaxy, like the Hydra-Centaurus supercluster and the Norma supercluster of galaxies,” said Karen Masters of the University of Portsmouth in England. She unveiled the map, which catalogs some 45,000 galaxies, on May 25 at a meeting in Boston of the American Astronomical Society.

Because the map encompasses nearly the entire sky rather than the smaller wedges revealed by previous surveys, it shows in new detail how clusters of galaxies congregate into vast walls and filaments, said Michael Hudson of the University of Waterloo in Canada. Hudson’s team has already used the data to find that a vast concentration of galaxies called the Shapley concentration is about twice as massive as previously estimated.

The largest galaxy concentrations trace the highest densities of dark matter — the invisible material believed to make up most of the cosmos’ mass. Hudson plans to use the map, which includes some galaxies as distant as 1 billion light-years, to examine the distribution of dark matter on scales up to 500 million light-years.

Redshift measurements, which gauge the amount by which cosmic expansion stretches light to longer wavelengths, provide the map’s critical third dimension, the distance of objects from Earth.

Masters and her colleagues have dedicated the map, based on data gathered by the 2MASS Redshift Survey, to John Huchra of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. Huchra, who died last year, pioneered the survey.

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