An international group of astronomers led by Ryan Foltz from the University of California at Riverside (USA) has found out why some of the galaxies entering galaxy clusters are mysteriously stopping the formation of new stars. This was announced in a press release on EurekAlert !.
Scientists have figured out how the process of fading took place in galaxies during most of the history of the universe. This allowed astronomers to determine the most likely reasons for the termination of star formation in galactic clusters.
For example, every galaxy that enters a cluster carries with it a certain amount of cold gas, which is the "raw material" for new stars. Hot, dense gas that already exists inside the cluster knocks out cold gas from the galaxy, stopping star formation.
Another possible mechanism is the cessation of the influx of cold gas into a galaxy that has entered a cluster. Finally, the energy released by the formation of stars can help the outflow of cold gas from the galaxy. In the latter scenario, the gas leaves the star system forever, which contributes to a much faster cessation of the formation of new stars than other mechanisms.
Researchers analyzed data on hundreds of galaxy clusters found in distant regions of the universe. The observations were carried out for 10 nights at the Keck Observatory (Hawaii) and 25 nights at the Gemini Observatory (Hawaii and Chile).
It turned out that as the Universe ages, it takes more and more time for galaxies to stop star formation in them. It currently takes five billion years, but in the early universe it took 1.1 billion years. This indicates that the main reason for stopping the birth of stars in massive galaxies is the knocking out of cold gas hot. However, in small galaxies, other mechanisms may play a major role.