It's typical for galaxies to thrive for billions of years. Some, however, are dropping off sooner than they should, and a new study has finally cracked the mystery.
In a study published in the Monthly Notices of the Royal Astronomical Society, researchers observed that galaxies that die young are shooting gas earlier, depleting themselves of the raw materials they need to live fully. All galaxies have a finite supply of raw materials and these dwindle as the years go by. It's just that some galaxies appear to be expending resources sooner than they should, leading to their early demise.
According to Ivy Wong, an astrophysicist from the University of Western Australia chapter of the International Centre for Radio Astronomy Research, two major types of galaxies exist. First, there are the blue galaxies still actively producing new stars. Then there are the red galaxies that have ceased growing.
Usually, galaxies go from being categorized as blue to red within at least two billion years. Some, however, are transitioning sooner, achieving red-galaxy status in under a billion years. Considering galaxies live for billions of years, death before reaching its one billionth birthday is very young.
To explore the reason behind the early deaths of galaxies, Wong and colleagues examined four galaxies that are close to reaching their limits producing stars, each one at a different stage. The researchers discovered that when close to meeting their limits, galaxies have a tendency to expel most of the gas they have.
Wong admitted it was difficult at first to use powerful telescopes for research because many astronomers don't believe that dying galaxies even have any gas remaining to be observed. The results of their study counters this idea, paving the way for increased access to telescopes which will allow the researchers to conduct larger surveys and discover specifically the premature shutdown that some galaxies undergo.
"One possibility is that it could be blown out by the galaxy's supermassive black hole," Wong said.
Another is that a neighboring galaxy could be responsible for ripping out the gas from another, although those observed by the researchers as part of the study did not have neighbors that could be stealing gas from them.
Researchers from the Institute for Astronomy, SKA South Africa, Yale University, Oxford Astrophysics, University of Hertfordshire and the University of Portsmouth also participated in the study titled "Misalignment between cold gas and stellar components in early-type galaxies."
