Astronomers find that galaxies are either asleep or awake
Astronomers have probed into the distant universe and discovered that galaxies display one of two distinct behaviors: they are either awake or asleep, actively forming stars or are not forming any new stars at all.
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Why galaxies turn off star formation is is one of the key questions in galaxy evolution, says Mariska Kriek, one of the paper’s co-authors from the Harvard-Smithsonian Center for Astrophysics and Princeton University. There are several theories, Kreik says, such as feedback by actively accreting black holes, mergers with other galaxies, or the halo in which the galaxy lives may become too hot for the gas to efficiently cool and form stars.
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“Next, we hope to determine whether galaxies go back and forth between waking and sleeping or whether they fall asleep and never wake up again,” van Dokkum said. “We’re also interested in how long it takes galaxies to fall asleep, and whether we can catch one in the act of dozing off.”
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