Large Sky Survey Reveals Dark Matter May Be Smoother Than Expected

9 December 2016, 9:04 am EST By Kalyan Kumar Tech Times
The map of dark matter from the KiDS survey, using ESO’s VLT Survey Telescope and revealing an expansive web of dense (light) and empty (dark) regions. The image is one among the five patches of the sky observed by KiDS.   ( Kilo-Degree Survey Collaboration / H. Hildebrandt & B. Giblin / ESO )

Distribution of dark matter in space is less dense than previously thought.

This surprising finding from a new galaxy survey also debunks the earlier findings of Planck satellite of European Space Agency that dark matter carries more density.

The paper carrying the findings titled "KiDS-450: Cosmological parameter constraints from tomographic weak gravitational lensing" has been published in the Monthly Notices of the Royal Astronomical Society.

Kilo-Degree Survey (KiDS) has shown how light from 15 million distant galaxies was affected by the gravitational influence of matter in the universe.

The survey was done with ESO's VLT Survey Telescope in Chile under the leadership of Hendrik Hildebrandt of Argelander-Institut für Astronomie in Bonn, Germany and Massimo Viola of Leiden Observatory in the Netherlands joined by a team of astronomers.

The analysis used images covering five patches of the sky that populated some 2,000 times the size of a full moon covering 15 million galaxies with an explicit focus on the effect of cosmic shear by using best image quality from the VST.

Weak Gravitational Lensing

Mapping the universe's dark matter has been the objective of all surveys including Kilo-Degree Survey, Hyper Suprime Cam, and Dark Energy Survey as they trace the phenomenon of weak gravitational lensing.

That phenomenon is defined as the slight distortion experienced on Galaxy images by the gravity of the intervening matter.

Kilo-Degree Survey, which studies the cosmic shear, has recorded 10 percent less effect than predicted by the standard cosmological model. This contradicts the Planck mission that insists dark matter being clumpy on the largest scales.

However, weak-lensing pioneer Tony Tyson from the University of California, Davis says a disagreement between KiDS and Planck is not a big deal.

In his reasoning, KiDS galaxies are more nearby than those in deeper surveys so the lensing signal will be correspondingly smaller.

Difference With Planck Data

The inconsistency with the results of the European Space Agency's Planck satellite was also explained by Viola who said the latest result indicates that dark matter in the cosmic web is holding a quarter of the universe but is less clumpy than previously believed.

Elusive to detection, dark matter is inferred only from its gravitational effects. That is why studies are the best way to determine the shape, scale, and distribution of that invisible material.

The new result will pave way for wider understanding of the universe and its evolution during the 14-billion-year history.

The disagreement with Planck results means astronomers have to reformulate their understanding of many aspects of the universe.

Hildebrandt said the findings will boost theoretical models on the universe's inception to the present day.

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