Galaxies study sheds light on dark matter

A study of distant galaxies has enabled astronomers to make the most accurate measurement to date of the large-scale structure of the universe.

Their findings support a theory that about 96 per cent of the Universe is made of elusive dark energy and dark matter.  In making their discovery, the international team including researchers at the University of Edinburgh, created the largest map so far of dark matter in the cosmos.  Their results draw on data collected during the first year of an international project called the Dark Energy Survey (DES).

Scientists taking part seek to better understand dark energy, which may be responsible for the accelerating expansion of the universe.  Their latest measurements of the amount and distribution of dark matter in the present-day cosmos are as precise as information captured previously about the early universe, by the European Space Agency’s orbiting Planck observatory.  Having both sets of data enables scientists to understand more about how the structure of the universe has evolved over 14 billion years.

For the latest study, researchers used data from a powerful dark energy camera on a telescope in Chile to create maps of galaxy positions as tracers and trace the density of dark matter.  They also precisely measured the shapes of 26 million galaxies, and used a technique called gravitational lensing – which accounts for light bending over large distances – to directly map the patterns of dark matter’s gravity over billions of light years.  To make these ultra-precise measurements, the DES team developed techniques to detect the tiny lensing distortions of galaxy images – which are invisible to the eye – enabling advances in understanding these signals.

The DES is a collaboration of more than 400 scientists from 26 institutions in seven countries.  Scientists at the participating Universities of Edinburgh, Cambridge, Manchester, Nottingham, Sussex, Portsmouth and UCL have led work central to the team’s results.

Their primary instrument, the 570-megapixel Dark Energy Camera, is mounted on the 4-metre Blanco telescope at the Cerro Tololo Inter-American Observatory in Chile.

UK researchers have led, over the years, major science analyses central to the results presented today.  DES scientists are using the camera to map one-eighth of the sky in unprecedented detail over five years.

The study was supported by the Science and Technology Facilities Council.

Dr Joe Zuntz of the University of Edinburgh reported: “The DES measurements, when compared with the Planck map, support the simplest version of the dark matter and dark energy theory.  This is a huge part of the puzzle of how the cosmos has evolved over the past 14 billion years.  It’s the dark Universe made visible on an unprecedented scale.