An international team of astronomers has discovered tidal debris in the galaxy group NGC 7232. The giant structure consists of cold neutral atomic hydrogen (HI) and extends about 450 thousand light years.
During the observation of a group of NGC 7232, consisting of at least 19 galaxies and is located at a distance of 78 million light-years (in the relative proximity of the Milky Way), the scientists used the radio telescope MeerKAT in South Africa. It turned out that the galaxies in the group actively interact with each other, which is expressed in various structures, such as tidal tails, bridges and other formations of stars and interstellar matter. These arise when tidal forces deform each galaxy, causing tails to drop off where stars continue to form.
In particular, astronomers have identified extended debris of cold, neutral atomic hydrogen around the core of a triplet galaxy known as NGC 7232/3 (composed of three spiral galaxies: NGC 7232, NGC 7232B and NGC 7233). The matter streams extend over 20 angular minutes, corresponding to 456 thousand light years, which is about three times the length of the neutral hydrogen atom region of the three galaxies.
Tidal debris contains HI with a total mass of 4.5 billion solar masses. This is more than half the total mass of hydrogen found in NGC 7232/3. NGC 7232/3, NGC 7233 and NGC 7232 have lost significant amounts of HI, while NGC 7232B appears to be characterized by an excess of gas. However, the scientists noted that, in general, the NGC 7232/3 triplet does not suffer from a deficit of atomic hydrogen involved in star formation, despite the tidal effects.
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