When galaxy stop creating stars die in a slow process that extends for about four billion years and that is leaving the cold gas needed to generate new stars.
This is the conclusion of a team of astronomers who investigated thousands of galaxies and deceased -vivas to assess whether this transition is fast or slow.
The blue galaxies are producing stars
Photo: Getty Images
In the dead galaxies detected elevated levels of metals that accumulated during training stars, and that point to a slow strangulation.
The study was published in the journal Nature.
“Metals are a powerful indicator of the history of the formation of stars. The more stars are born in a galaxy, the metal content can be detected” Yingjie said Peng, a professor at the University of Cambridge and lead author of the study.
“In this way, observing the levels of metals in the dead galaxies could give us an indication of how they died.”
If the death of a galaxy was swift and violent that is, if you saw the cold stripped gas allowing the formation of stars from internal causes or external-would cease immediately create stars and metal content would remain the same.
But if the galaxy ceases to have their gas supplies but continues to use the one that fits, the metal would continue to increase until eventually, “suffocate”.
CO2 in humans, galaxies metal
Andrea Cattaneo, Observatoire de Paris in France, compared This evidence high levels of carbon dioxide in a strangled human body.
“For (the throttling process), they are used all the oxygen that remains in the lungs and continues to produce carbon dioxide, which is trapped in the body,” he said Cattaneo to Nature.
“Instead of accumulating CO2, the stifled galaxies accumulate heavier than helium produced by giant stars metals-elements”.
The team led by Peng discovered the accumulation of metals by comparing the spectrum of light emitted by 23,000 passive red galaxies with 4,000 blue galaxies were forming stars.
The researchers used data from the Sloan Digital Sky Survey, a vast collection of detailed and colorful images covering a third of the sky that has been used to compile an accurate 3D map of the universe.
The red galaxies are no longer able to create stars
Photo: Getty Images
Suspects
On average, they live four billion galaxies were younger than the dead years.
According to the calculations of astronomers, this is equivalent to the time that the galaxies needed to burn the gas that remains in the strangulation.
It is considerably longer than the four minutes it takes for the body to die for the same cause within, but the analogy holds.
“This is the first conclusive evidence that galaxies are being strangled until they die,” says Peng.
“The next step is to understand what causes this process. In essence, we know the cause of death, but we do not know who the murderer is, but we have some suspects.”
One of the possible culprits is overpopulation. If a galaxy is a large group, gathering gas from the surrounding environment it can be affected and begin the process of strangulation.
In galaxy clusters, the astronomers saw even more pronounced differences in metal content, giving more weight to this idea.
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