A duo of scientists at the University of Waterloo, Canada, has been able to capture the first composite image of a dark matter bridge that connects galaxies together. The image confirms predictions that galaxies across the Universe are tied together through a cosmic web connected by dark matter that has until now remained unobservable.
Dark matter filaments (shown in red) bridge the space between galaxies (shown in white) on this false color map. Image credit: Seth Epps & Michael Hudson, University of Waterloo.
“For decades, researchers have been predicting the existence of dark-matter filaments between galaxies that act like a web-like superstructure connecting galaxies together,” said Prof. Mike Hudson, from the Department of Physics and Astronomy at the University of Waterloo.
“This image moves us beyond predictions to something we can see and measure.”
Prof. Hudson and his colleague, Seth Epps, used a technique called weak gravitational lensing, an effect that causes the images of distant galaxies to warp slightly under the influence of an unseen mass such as a planet, a black hole, or in this case, dark matter.
The effect was measured in images from a multi-year sky survey at the Canada-France-Hawaii Telescope.
The researchers combined lensing images from more than 23,000 pairs of galaxies located approximately 4.5 billion light-years away to create a composite image that shows the presence of dark matter between the two galaxies.
The results show the dark matter filament bridge is strongest between systems less than 40 million light-years apart.
“By using this technique, we’re not only able to see that these dark matter filaments in the Universe exist, we’re able to see the extent to which these filaments connect galaxies together,” Epps said.
The research is published in the Monthly Notices of the Royal Astronomical Society (arXiv.org preprint).
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Seth D. Epps & Michael J. Hudson. 2017. The weak-lensing masses of filaments between luminous red galaxies. Mon Not R Astron Soc 468 (3): 2605-2613; doi: 10.1093/mnras/stx517
This article is based on text provided by the University of Waterloo.
