Cambridge: Cause of Galactic Death: Strangulation

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Cambridge: Cause of Galactic Death: Strangulation

Post by bystander » Thu May 14, 2015 9:43 pm

Cause of Galactic Death: Strangulation
University of Cambridge | 2015 May 13

Astronomers have partially solved an epic whodunit: what kills galaxies so that they can no longer produce new stars?
[attachment=0]strangulation.jpg[/attachment][hr][/hr]
As murder mysteries go, it’s a big one: how do galaxies die and what kills them? A new study, published today in the journal Nature, has found that the primary cause of galactic death is strangulation, which occurs after galaxies are cut off from the raw materials needed to make new stars.

Researchers from the University of Cambridge and the Royal Observatory Edinburgh have found that levels of metals contained in dead galaxies provide key ‘fingerprints’, making it possible to determine the cause of death.

There are two types of galaxies in the Universe: roughly half are ‘alive’ galaxies which produce stars, and the other half are ‘dead’ ones which don’t. Alive galaxies such as our own Milky Way are rich in the cold gas – mostly hydrogen – needed to produce new stars, while dead galaxies have very low supplies. What had been unknown is what’s responsible for killing the dead ones.

Astronomers have come up with two main hypotheses for galactic death: either the cold gas needed to produce new stars is suddenly ‘sucked’ out of the galaxies by internal or external forces, or the supply of incoming cold gas is somehow stopped, slowly strangling the galaxy to death over a prolonged period of time. ...

Strangulation as the primary mechanism for shutting down star formation in galaxies - Y. Peng, R. Maiolino, R. Cochrane
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Artist’s impression of one of the possible galaxy strangulation mechanisms: <br />star-forming galaxies (fed by gas inflows) are accreted into a massive hot <br />halo, which ‘strangles’ them and leads to their death. (Credit: re-active)
Artist’s impression of one of the possible galaxy strangulation mechanisms:
star-forming galaxies (fed by gas inflows) are accreted into a massive hot
halo, which ‘strangles’ them and leads to their death. (Credit: re-active)
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