A small group of astronomers have found a new way to ‘see’ the elusive dark matter halos surrounding galaxies, with a new technique 10 times more accurate than the good method. most before. Works are published in Royal Astronomical Society monthly announcement.
Scientists currently estimate that up to 85% of the mass in the universe is invisible. This ‘dark matter’ cannot be observed directly, as it does not interact with light in the same way as ordinary matter that makes up the stars, planets and life on Earth.
So how do we measure what cannot be seen? It is important to measure the effect of the gravitational force that dark matter exerts.
“It’s like looking at a flag trying to know how much wind is,” explains Pol Gurri, a graduate student at Swinburne University of Technology, who led the new study. You can’t see the wind, but the movement of the flag tells you how hard the wind is blowing ”.
The new study focuses on an effect called the weak gravitational lens, a feature of Einstein’s general theory of relativity. “Dark matter will slightly distort the image of whatever is behind it,” said Associate Professor Edward Taylor, who was also involved in the study. “The effect is a bit like reading newspaper through the bottom of a wine glass.”
A weak gravitational lens has been one of the most successful ways to map the dark matter content of the Universe. Now, the Swinburne team has used the 2.3m ANU Telescope in Australia to map how galaxies with gravitational lenses are rotating. “Because we know the stars and gas are supposed to move inside galaxies, we know roughly what that galaxy will look like,” Gurri said. “By measuring the amount of distortion in the real galactic image, we can then find out how much dark matter to explain what we see.”
This new study shows how this velocity information allows for much more precise measurement of lens effects than just using shape. “With a new view of dark matter,” Gurri said, “we hope to get a clearer picture of where dark matter is and what its role is in how galaxies form.”
Future space missions such as NASANancy Grace’s Roman Space Telescope and the European Space Agency’s Euclid Space Telescope are partly designed to make these types of measurements based on the shapes of hundreds of millions of galaxies. “We have shown that we can make a real contribution to these global efforts with a relatively small telescope built in the 1980s, just by thinking about it,” said Taylor. deals in a different way.
Reference: “Precise weak lens first shear force measurements” by Pol Gurri, Edward N Taylor and Christopher J Fluke, September 21, 2020, Royal Astronomical Society monthly announcement.
DOI: 10.1093 / mnras / staa2893