Galaxies Are Being Killed Throughout The Universe. What's Killing Them?

There seems to be a serial killer at large in the universe — a galaxy strangler — and astronomers are scrambling to identify the culprit, reports

A study of 11,000 galaxies has shown that many of them are having their gas aggressively stripped away. Since gas is essential to star formation, a galaxy's lifeblood, the phenomenon is a swift killer, and so far scientists have been at a loss to explain it. But new research by a global team of researchers based at the International Centre for Radio Astronomy Research (ICRAR) may have narrowed down the list of suspects.

Their study has shown that something called "ram-pressure stripping" appears to be at play on a scale much larger than previously thought. Basically, galaxies are believed to be surrounded by clouds of invisible dark matter, and moving through these clouds can cause a drag force that strips them of their gas. This force is most prevalent in large galaxy clusters, as galaxies pass through the superheated plasma that coalesces in the intracluster medium.

"You can think of it like a giant cosmic broom that comes through and physically sweeps the gas from the galaxies, we've found this removal of gas by stripping is potentially the dominant way galaxies are quenched by their surrounds, meaning their gas is removed and star formation shuts down." explained team leader Toby Brown, who is also a Ph.D. candidate at ICRAR and Swinburne University of Technology.

The research revealed that ram-pressure stripping is not just occurring within large galaxy clusters; it's happening in small ones too. It's an alarming process because it can strip a galaxy of its gas fairly quickly, on the order of tens of millions of years. On astronomical timescales, that's the drop of a hat.

"If you remove the fuel for star formation, then you effectively kill the galaxy and turn it into a dead object," said Brown.

The researchers work was published in the Monthly Notices of the Royal Astronomical Society.





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