Collisions can deprive galaxies of dark matter

Collisions between dwarf galaxies can cause them to lose all dark matter. This is stated in an article published in a recent issue of the journal Nature by an international team of astrophysicists.

Galaxies without dark matter

In 2018, astronomers discovered an unusual galaxy in the vicinity of the Milky Way, designated NGC 1052-DF2. With similar sizes to our galaxy, it contains 200 times fewer stars. At the same time, there is practically no dark matter in it — a substance that does not participate in electromagnetic interaction and is inaccessible to direct observation. Its presence can be determined only by the gravitational effect on visible matter.

Galaxy NGC 1052-DF2. Source: SCIENCE: NASA, ESA, STScI, Zili Shen (Yale), Pieter van Dokkum (Yale), Shany Danieli (IAS) IMAGE PROCESSING: Alyssa Pagan (STScI)

The discovery came as a surprise to astronomers. It is believed that dark matter is a key component necessary for the formation of galaxies. Without it, the primary gas would not have sufficient gravitational attraction to begin to contract and form the first “star islands”. A year later, astronomers discovered another “empty” galaxy containing almost no dark matter. It was named NGC 1052-DF4. The discovery provoked new discussions about the mechanisms of the origin of the first star systems and the correctness of existing models.

Mechanism of dark matter loss

In an attempt to explain the existence of galaxies without dark matter, an international team of astrophysicists has expanded the research of other groups that have found traces of the separation of dark and normal matter on a large scale during collisions of galactic clusters. They came to the conclusion that such a mechanism could lead to the appearance of galaxies found without dark matter. Since dark matter does not interact with itself or ordinary matter, in the event of a galactic collision, it can “fly out” beyond its galaxy and continue moving through space.

Diagram showing a possible mechanism for the formation of galaxies without dark matter. Source: Nature (2022). DOI: 10.1038/s41586-022-04665-6

The probability of such a scenario confirms that NGC 1052-DF2 and NGC 1052-DF4 are moving away from each other and there are several other dwarf galaxies next to them that can be lined up in a single line. This suggests that they may have the same origin.

According to

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