ICRAR: Galaxy Murder Mystery

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bystander
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ICRAR: Galaxy Murder Mystery

Post by bystander » Tue Jan 17, 2017 5:29 pm

Galaxy Murder Mystery
International Centre for Radio Astronomy Research | 2017 Jan 17
[img3="This artist’s impression shows the spiral galaxy NGC 4921 based on observations by Hubble. Credit: ICRAR, NASA, ESA, the Hubble Heritage Team (STScI/AURA)"]http://s3-ap-southeast-2.amazonaws.com/ ... 4x1024.jpg[/img3][hr][/hr]
It’s the big astrophysical whodunit. Across the universe, galaxies are being killed and the question scientists want answered is, what’s killing them?

New research published today by a global team of researchers, based at the International Centre for Radio Astronomy Research (ICRAR), seeks to answer that question. The study reveals that a phenomenon called ram-pressure stripping is more prevalent than previously thought, driving gas from galaxies and sending them to an early death by depriving them of the material to make new stars.

The study of 11,000 galaxies shows their gas -- the lifeblood for star formation -- is being violently stripped away on a widespread scale throughout the local universe.

Dark matter is the mysterious material that despite being invisible accounts for roughly 27 percent of our universe, while ordinary matter makes up just 5 percent. The remaining 68 percent is dark energy.

“During their lifetimes, galaxies can inhabit halos of different sizes, ranging from masses typical of our own Milky Way to halos thousands of times more massive,” Mr. Brown said.

“As galaxies fall through these larger halos, the superheated intergalactic plasma between them removes their gas in a fast-acting process called ram-pressure stripping. ...

Cold Gas Stripping in Satellite Galaxies: From Pairs to Clusters - Toby Brown et al
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Ann
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Re: ICRAR: Galaxy Murder Mystery

Post by Ann » Tue Jan 17, 2017 6:48 pm

Like Earthandsky, I question the use of "murder" in this context, but for another reason. Galaxies that are deprived of starforming material don't die. They are very much still here. Consider huge elliptical galaxy M87. It is known as a "red and dead" galaxy, because it has no appreciable star formation, but it packs a whopper of a punch when it comes to mass, and even when it comes to luminosity.

We are often taught that "ordinary", baryonic matter (the stuff that makes stars, planets and people) is only the tip of the iceberg of the universe, which is made mostly of dark matter and dark energy. Well, the brilliant blue stars that are the hallmark of starforming galaxies are just the tip of the iceberg when it comes to the total baryonic mass of the galaxies. The little red stars that fill the galaxies are not only a dime a dozen, they are as common as dirt, and their collective mass is just huge - and I have to wonder if they are not planning to live longer than the universe!

It is clear beyond a doubt that star formation in the universe is winding down fast, but that doesn't mean that the galaxies are going away!

Ann
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