Scientists have discovered galaxies NGC 1052-DF2 and DF2 that contain almost no dark matter – an invisible substance that fills almost the entire Universe.
In two new scientific papers, researchers led by Pieter van Dokkum, a professor of astronomy at Yale University, USA, show that dark matter is generally separable from galaxies containing normal matter.
In the first of these studies, the team confirmed the results of their initial observations of the galaxy NGC 1052-DF2, which show that dark matter is almost completely absent in the galaxy. Using the Keck Cosmic Web Imager (KCWI) tool at the Observatory. Keke, located in Hawaii, the researchers conducted more accurate measurements and confirmed that the globular clusters of stars in this galaxy really move at speeds that can be explained by the presence of only normal matter. If dark matter were present in the DF2 galaxy, these clusters of stars would move at a much higher speed.
The KCWI tool is unique because of the combination of a wide viewing angle and high spectral resolution. This tool not only allows you to see the galaxy as a whole, but its high resolution allows you to accurately measure the mass of the galaxy.
-Shany Danieli, a graduate student at Yale University and the main author of the first paper on the DF2 galaxy
In the second of the research papers presented by the team, headed by van Dockum himself, another low-matter galaxy, called NGC 1052-DF4, or abbreviated as DF4, was discovered using the Low Resolution Imaging Spectrometer (LRIS) tool.
The discovery of a second galaxy devoid of dark matter has become even more inspiring than the discovery of the first galaxy. This means that the chances of finding such galaxies are higher than previously thought. Since we could not reveal the reasons for the formation of such galaxies, we hope that this will inspire other researchers to conduct new theoretical studies on this issue.
-Shany Danieli
Like DF2, the DF4 galaxy belongs to the ultradiffuse galaxies (UDGs) class, which is relatively new for astronomers. These galaxies are about the same size as the Milky Way, but contain hundreds of times smaller stars.
Unusual galaxies like NGC 1052-DF2 challenge the dark matter hypothesis
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