With the telescope MeerKAT astronomers recorded a large number of cold neutral atomic water in the group of galaxies NGC 7232. In the opinion of the scientists, this indicates a complementary relationship between galaxies. The preprint of this article is available at arXiv.org.

Group of galaxies NGC 7232 and a triplet of galaxies. B. Namumba et al.
NGC 7232 group of galaxies and a triplet of galaxies. B. B. Namumba et al.
What is known about galaxy groups?

It is widely known that such properties of galaxies as morphology, gas content and formation of stars are influenced by the interaction between galaxies and their medium. Most galaxies in the near universe are in small groups. The interrelationship of their elements can be studied by the size and shape of tidal tails, bridges and other tidal devices. In the hierarchical scenario, groups of galaxies are the building blocks of large galactic assemblages. There is an assumption that before forming galaxy assemblages galaxies must undergo some preliminary treatment (e.g., change the shape or gas volume) through a tidal interaction. Thus, some finite properties of galaxies, which we witness in the assemblages, were created due to the processes that were overblown by the formation of the assemblages and took place in very different conditions.

What did they find out?

Astronomers have recorded vast neutral atomic streams near the triple galaxy NGC 7232/3. The structure is more than 140 kiloparsecs (457 thousand light years) long and has a mass of water approaching 4.5 billion solar masses, which is more than half of the total mass of neutral nuclear water in the triple. In addition, the shape of the galaxies included in the triplet is sporadic, which indicates an interaction between them. Astronomers also noticed that, unlike NGC 7232B, NGC 7232 and NGC 7233 have lost most of their calculated atomically neutral water mass. The velocities of NGC 7233 and NGC 7232 are equal to the velocities of tidal waves on the water. Thus, the researchers concluded that NGC 7232B did not lose much gas in the medium in the middle of the triplet and that most of these additional tidal tides originated from the pair of galaxies NGC 7233 and NGC 7232.

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