The new map was released Monday at the April meeting of the American Physical Society in Baltimore, Md. It was created using data captured by the Dark Energy Camera, a 570-megapixel imaging device that is the primary instrument for the Dark Energy Survey (DES), according to a press release.
Dark matter, the mysterious substance that makes up roughly a quarter of the universe, is invisible to even the most sensitive astronomical instruments because it does not emit or block light. But its effects can be seen by studying a phenomenon called gravitational lensing -- the distortion that occurs when the gravitational pull of dark matter bends light around distant galaxies. Understanding the role of dark matter is part of the research program to quantify the role of dark energy, which is the ultimate goal of the survey.
This analysis was led by Vinu Vikram of Argonne National Laboratory (then at the University of Pennsylvania) and Chihway Chang of ETH in Zurich. Vikram, Chang and their collaborators at Penn, ETH Zurich, the University of Portsmouth, the University of Manchester and other DES institutions worked for more than a year to carefully validate the lensing maps.
"We measured the barely perceptible distortions in the shapes of about two million galaxies to construct these new maps," Vikram said, according to the press release. "They are a testament not only to the sensitivity of the Dark Energy Camera, but also to the rigorous work by our lensing team to understand its sensitivity so well that we can get exacting results from it."
The dark matter map makes use of early DES observations and cover only about three percent of the area of sky DES will document over its five-year mission. The survey has just completed its second year. As scientists expand their search, they will be able to better test current cosmological theories by comparing the amounts of dark and visible matter.
"Our analysis so far is in line with what the current picture of the universe predicts," Chang said, according to the press release. "Zooming into the maps, we have measured how dark matter envelops galaxies of different types, and how together they evolve over cosmic time. We are eager to use the new data coming in to make much stricter tests of theoretical models."
The Dark Energy Survey is a collaboration of more than 300 scientists from 25 institutions in six countries. Its primary instrument, the Dark Energy Camera, is mounted on the 4-meter Blanco telescope at the National Optical Astronomy Observatory's Cerro Tololo Inter-American Observatory in Chile, and its data is processed at the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign.
Funding for the DES has been provided by the U.S. Department of Energy Office of Science, the U.S. National Science Foundation, the Ministry of Science and Education of Spain, the Science and Technology Facilities Council of the United Kingdom, the Higher Education Funding Council for England, ETH Zurich for Switzerland, the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign, the Kavli Institute of Cosmological Physics at the University of Chicago, Financiadora de Estudos e Projetos, Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, Conselho Nacional de Desenvolvimento Científico e Tecnológico and the Ministério da Ciência e Tecnologia, the Deutsche Forschungsgemeinschaft and the collaborating institutions in the Dark Energy Survey. The DES participants from Spanish institutions are partially supported by MINECO under grants AYA2012-39559, ESP2013-48274, FPA2013-47986 and Centro de Excelencia Severo Ochoa SEV-2012-0234, some of which include ERDF funds from the European Union.
