The galaxies we see falls on either one of the two groups: “alive”, this means that a galaxy is still capable of creating stars and “dead” if not. But how do galaxies die? A new report by astronomers at the University of Cambridge, distributed in Nature, says that the galaxies were slowly strangled to death rather than being declared unproductive by an intergalactic event or intrusive astronomical object.
Cold hygiene (i.e. not hot and bursting) — in stellar quantities is one of the essential things to produce new stars. By tracing the levels of this and other necessary components in thousands of galaxies watched by the Sloan Digital Sky Survey, researchers could find out whether that star-forming material is running out or rendered completely unusable.
“We found that for a given stellar mass, the metal content of a dead galaxy is significantly higher than a star-forming galaxy of similar mass,” said study co-author Roberto Maiolino. “This isn’t what we’d expect to see in the case of sudden gas removal, but it is consistent with the strangulation scenario.”
Other variables supported the strangulation theory, such as those star-forming galaxies were regularly 4 billion years younger than dead ones, scores from the researchers ‘estimates of how fast the galaxies’ materials would be consumed.
The strangler’s identity or whether there really is one is still a mystery.
“This is the first conclusive evidence that galaxies are being strangled to death,” said lead author Yingjie Peng. “What’s next though, is figuring out what’s causing it. In essence, we know the cause of death, but we don’t yet know who the murderer is, although there are a few suspects.”