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Astronomers confirm the existence of galaxies without dark matter



  Galaxies without dark matter

A photo of the DF2 galaxy (Photo credit: NASA, ESA and P. van Dokkum [Yale University])

A Yale-led research team doubles its earlier version of finding a galaxy with almost no dark Matter.

In 201

8, researchers published their original study of the galaxy NGC 1052-DF2 – DF2 for short – the first known galaxy to contain little or no dark matter. The finding was important because it showed that dark matter is not always associated with traditional matter at the galactic level. Several theories have also been excluded, according to which dark matter is not a substance, but a manifestation of the laws of gravity on a cosmic scale.

Invisible dark matter typically dominates the composition of galaxies. Finding an object without dark matter was unprecedented and led to heated discussions within the scientific community.

"If there is an object, you always have a small voice in the back of your mind and say," But what if you say "Are you wrong?" Said team leader Pieter van Dokkum, professor of astronomy Sol Goldman family in Yale. "Although we made all the checks we could imagine, we were worried that nature had thrown us in a loop and conspired to make something really special while it was really something Everyday was. "

Well, a couple of New Studies published in The Astrophysical Journal Letters support the team's initial statement.

" The fact that we see something completely new is fascinating. " Yale student Shany Danieli, who first discovered the galaxy over two years ago. "Nobody knew there were such galaxies, and the best thing for an astronomy student in the world is to discover an object, be it a plan et, a star or a galaxy nobody knew or thought about. "19659004] Danieli is the lead author of one of the new studies. It confirms the team's first observations on DF2 based on more accurate measurements from the W.M. Keck Cosmic Web Imager by Keck Observatory. The researchers found that the stars within the galaxy are moving at a speed that corresponds to the mass of normal matter in the galaxy. If dark matter were present in DF2, the stars would move much faster.

Van Dokkum is the lead author of the other new study describing the discovery of a second galaxy without dark matter. This galaxy is called DF4.

"The discovery of a second galaxy with very little or no dark matter is as exciting as the first discovery of DF2," said van Dokkum. "This means that the chances of finding more of these galaxies are higher than we previously thought. Since we have no good ideas for the formation of these galaxies, I hope these discoveries will encourage more scientists to work on this puzzle. "

Both DF2 and DF4 are part of a relatively new class of galaxies called ultra-diffuse galaxies (UDGs). They are the size of the Milky Way, but have between 100 and 1,000 times fewer stars. This makes them fluffy and translucent – and hard to watch.

Ironically, the lack of dark matter in these UDGs reinforces the case for dark matter, the researchers say. It proves that dark matter is a substance that is not coupled with normal matter because it is found separately.

The team members include van Dokkum and Danieli as well as Roberto Abraham from the University of Toronto, Aaron Romanowsky from San Jose State University and Charlie Conroy from Harvard.

Danieli conducts a large-scale survey with the Dragonfly Telephoto Array – a telescope designed by van Dokkum – to systematically search for further examples and then re-observe the candidates with the Keck telescopes

"We hope to Next, find out how common these galaxies are and if they exist in other parts of the universe, "Danieli said. "We want to find more evidence to understand how the properties of these galaxies work with our current theories. We hope that this will take us a step further to understand one of the greatest mysteries of our universe – the nature of dark matter.

Publications:

  • Shany Danieli et al.: "Dark matter still missing: KCWI stellar kinematics with high resolution of NGC1052-DF2," ApJL, 2019; doi: 10.3847 / 2041-8213 / ab0e8c
  • Pieter van Dokkum. et al., "A Second Galaxy Lacks Dark Matter in the NGC 1052 Group," ApJL, 2019; doi: 10.3847 / 2041-8213 / ab0d92


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