An international team of scientists has unveiled detailed maps of dark matter dynamics in the nearby Universe. The research is published in the Journal of Cosmology and Astroparticle Physics (arXiv.org preprint).

Dark matter is the mysterious substance that makes up roughly a quarter of the Universe.

It is invisible to even the most sensitive astronomical instruments because it does not emit or block light.

“As it does not emit or react to light, its distribution and evolution are not directly observable and have to be inferred,” said lead author Dr. Florent Leclercq, from the Institute of Cosmology and Gravitation at the University of Portsmouth, UK.

Dr. Leclercq and his colleagues from the Technische Universität München, the Institut d’Astrophysique de Paris, the Institut Lagrange de Paris, the University of Illinois at Urbana-Champaign, and the University of Portsmouth analyzed data obtained during 2000-2008 from the Sloan Digital Sky Survey (SDSS).

The SDSS survey has deep multi-color images of one fifth of the sky and spectra for more than 900,000 galaxies.

The team used a set of phase-space analysis tools and built on research from 2015, which reconstructed the initial conditions of the nearby Universe.

“We present a cosmographic analysis of the dark matter distribution and its evolution, referred to as the dark matter phase-space sheet, in the nearby Universe as probed by the SDSS main galaxy sample,” the authors said.

“Our method provides extremely accurate estimates of nearby density and velocity fields, even in regions of low galaxy density.”

“It also measures the number of matter streams, and the deformation and parity reversals of fluid elements, which were previously thought inaccessible using observations.”

“We illustrate the approach by showing the phase-space structure of known objects of the nearby Universe such as the Sloan Great Wall, the Coma cluster and the Boötes void.”

The new dark matter maps cover the Northern Sky up to a distance of two billion light-years.

“Adopting a phase-space approach discloses a wealth of information, which was previously only analyzed in simulations and thought to be inaccessible using observations,” Dr. Leclercq said.

“Accessing this information in galaxy surveys opens up new ways of assessing the validity of theoretical models in light of observations.”

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Florent Leclercq et al. The phase-space structure of nearby dark matter as constrained by the SDSS. JCAP 2017 (6): 049; doi: 10.1088/1475-7516/2017/06/049