Once they stop making new stars, a galaxy is considered ‘dead’ as there comes a time when these galaxies run out of gas to form new stars. As such, they will gradually become redder as bright blue stars turn into supernovae, leaving smaller and fainter stars behind. It is not something strange or unusual. It is an event that will take place in all galaxies. However, despite its normality, astronomers had never clearly seen the beginning of this process of a galaxy about to die in the early universe.
Up to now.
An international team of astronomers has captured a fabulous image of a dying galaxy, expelling 10,000 suns worth of gas each year due to a major collision. The research, led by the University of Durham (England ) examined 9 billion years in the past for evidence that mergers of galaxies in the early universe could stop star formation. These mergers force the galaxy’s gas leakage and weaken its ability to form new stars, effectively marking the end of its life as an active body, as we explained at the beginning.
The astronomers used the ALMA ( Atacama Large Millimeter / submillimeter Array ) telescope located in the desert region of Chile to detect a distant galaxy in which a massive gas ejection is progressing. And they found ID2299, which is expelling about half of its reservoir of cold gas out of the galaxy. This is the first time that a typical massive star-forming galaxy has been observed in the distant universe about to ‘die’ due to a massive ejection of cold gas.
Thus, astronomers stumbled upon this dying galaxy by mere accident. While observing a hundred galaxies in distant places, they noticed something strange precisely in galaxy ID2299. They watched it for a few minutes: the galaxy had a tail of gas that was being ejected , which is precisely the snapshot (artistic recreation, of course) that accompanies this article. The gas was being expelled at a surprising rate, the equivalent of 10,000 soles a year.
That loss is removing 46% of all cold gas from the galaxy. Between this and the intense star formation, ID2299 will run out of gas in just a few tens of millions of years. Something that is surprising especially considering that it is going through this event only 4.5 billion years after the Big Bang, just after the moment in which the galaxies produced stars at incredible speeds, in their most active phase.
“ We still don’t know what the exact processes are behind the disconnection of star formation in massive galaxies. Feedback-driven winds from star formation or active black holes are believed to be primarily responsible for expelling gas and stifling growth. Our research provides evidence that the gas launched from ID2299 has likely been ejected by the tides due to the merger between two gas-rich galaxies, ”explains Annagrazia Puglisi, Center for Extragalactic Astronomy at Durham University and leader of the work published in the journal Nature Astronomy.
Referencia: Puglisi, A., Daddi, E., Brusa, M. et al. A titanic interstellar medium ejection from a massive starburst galaxy at redshift 1.4. Nat Astron (2021). https://doi.org/10.1038/s41550-020-01268-x
