Traces of the collision of a galaxy without dark matter with its neighbor have been discovered
(ORDO NEWS) — For the first time, an international team of astronomers has found direct evidence that dwarf galaxies, almost completely devoid of dark matter, sometimes collide with larger neighbors.
This potentially explains the absence of dark matter and cold gas inside them.
In recent years, astronomers have discovered about two dozen galaxies in which dark matter is either completely absent or present in small quantities.
Due to the extremely low density of matter, researchers began to call them “super-dispersed galaxies” (UDGs).
A large number of such discoveries forced astronomers to actively study UDGs and look for explanations for their existence.
So far, scientists have come to a consensus about how “super-scattered galaxies” arise. Some observations indicate that some of the UDGs lost their dark matter reserves as a result of collisions with larger galaxies, while photographs of other similar objects indicate that they formed at a great distance from other galaxies and could not interact with them.
History of galaxy collisions
Zemaitis and his colleagues have discovered the first solid evidence that UDGs can still arise from the interactions of dwarf galaxies with larger objects.
Scientists came to such conclusions during observations of the “super scattered galaxy” F8D1, located in the constellation Ursa Major at a distance of 11 million light-years from the Milky Way.
This dwarf galaxy is located at a relatively short distance from the large spiral galaxy M81, which led the researchers to the idea that both objects could have collided with each other in the distant past.
To search for traces of these gravitational interactions, astronomers obtained detailed photographs of the F8D1 and M81 galaxies using instruments from the 8.2-meter Subaru Telescope in Hawaii.
Subsequent analysis of these images indicated the presence of a kind of giant “tail” of stars that stretched between the galaxy F8D1 and M81.
The length of this stream of luminaries is about 200 thousand light years, and inside it, according to researchers, there are several million stars that in the distant past were part of a “super-scattered galaxy.”
As astronomers’ calculations show, these luminaries were thrown out of F8D1 as a result of gravitational interactions with M81 and a potential collision between these objects that occurred one or two billion years ago.
This suggests that at least some of the “super-scattered galaxies” lost their reserves of dark matter as a result of interactions with larger neighbors, the scientists concluded.
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