Most star-forming galaxies are embedded within a cloud of cold neutral hydrogen gas, which acts as the raw fuel from which stars can eventually form. This gas is extremely faint, and can only be detected in radio wavelengths. It is diffuse, and extends beyond the visible part of the galaxy. By observing this hydrogen gas, astronomers are able to understand the evolutionary processes that take place in galaxies.
The majority of galaxies in the Universe reside in groups. However, it is rare to detect a group with such a large number of group members with so much neutral hydrogen. This suggests that the group is still in the process of assembly, as it has not undergone evolutionary processes that would remove this gas from the galaxies.
The paper was led by Shilpa Ranchod, an MSc student supervised by Prof. Roger Deane at the University of Pretoria. “The distribution of neutral hydrogen gas in these galaxies has revealed interesting, disturbed morphologies suggesting that these galaxies are group members, and are being influenced by their cosmic neighbours in the group”, notes Ranchod. “For example, we found an interacting pair of galaxies that will potentially merge to form a new galaxy with a completely transformed appearance.”
This galaxy group was discovered by the MeerKAT International Gigahertz Tiered Extragalactic Exploration (MIGHTEE) survey. It is one of the large survey projects in progress with South Africa’s MeerKAT telescope and involves a team of South African and international astronomers.
The MeerKAT radio telescope in the Northern Cape, South Africa’s precursor to the Square Kilometre Array (SKA), aims to answer fundamental questions about the formation and evolution of galaxies. Its exceptional sensitivity provides astronomers with further insight into the drivers of galaxy evolution.