UNIVERSE. It contains hundreds of billions of galaxies.
MADRID, EFE
Like a thriller it were, experts point out just the ‘bottleneck’ as the leading cause of galactic death that occurs after that galaxies are deprived of the raw materials needed to create new stars.
The levels of metals containing the dead galaxies provide a key fingerprint that makes it possible to determine the cause of his death until now was unknown, according to a study published in Nature by researchers at the University of Cambridge and the Royal Observatory in Edinburgh.
In the universe there are two types of galaxies, nearly half are ‘alive’ galaxies, including the Milky Way that is rich in cold gas, mostly hydrogen, they need to create new stars.
The other galaxies are ‘dead’, ie they can not create stars and also the concentration of cold gas is very low, but until now it was not known what caused the death of galaxies, recalls the study .
The astronomers had advanced two main hypotheses to explain the galactic death or cold gas is sucked suddenly out of the galaxy by internal or external forces, or the supply of cold gas somehow stops “slowly strangling the galaxy, for a period of time until death.”
The researchers used data from the Sloan Digital Sky Survey to analyze the levels of metals in more than 26,000 galaxies in size environment.
“Metals are a powerful marker in the history of the formation of stars. The more stars are born in a galaxy metal content can be detected, “said Cavendish Laboratory and professor at the Kavli Institute for Cosmology at the University of Cambridge, Yingjie Peng, lead author of the study.
Therefore, by looking at the levels of metals in the dead galaxies should be possible to know how they died, he said.
If galaxies are ‘killed’ by a sudden gas outlet cold outside the galaxy, then the content metal of a dead galaxy should be the same as it was just before his death, for the formation of stars would stop abruptly.
However, in the case of death by strangulation star formation can continue while the cold gas is not extinguished entirely.
The researchers analyzed statistics content of cold gas differences between living galaxies and dead, allowing them to determine the cause of death Most medium-size galaxies.
Professor Roberto Maiolino, one of the study authors, said they have determined that the content of metals in a dead galaxy is “significantly higher” than in a living with a similar mass.
“This is not what you expect to see in the case of sudden gas extraction and is consistent with the scenario of strangulation,” he said.
Researchers They tested their hypothesis by observing the difference of stellar age between living galaxies and dead, regardless of the level of the metals they contain, and found a difference of 4,000 million years, which is in line with the time it would take a vivid galaxy die . by strangulation
“This is the first conclusive evidence that galaxies are strangled to death, Peng, who said said:”. Yet know who the murderer, although we have some suspects “
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