Astronomers hunt for elusive galaxy killer

Here’s a mysterious epidemic going on in the surrounding cosmos. Galaxies are dying premature deaths — disappearing for unexplained reasons.

Who or what is killing off all these galaxies? Astronomers want answers.

In a new study, scientists with the International Center for Radio Astronomy Research, ICRAR, suggest ram-pressure stripping is more prevalent than previously thought. ICRAR is a joint venture between Curtin University and the University of Western Australia.

A survey of some 11,000 galaxies showed gas is being stolen from thousands of galaxies. Without gas, the galaxies cannot forge new stars and begin to die.

What do all these withering galaxies have in common? Researchers believe they’re all situated within halos of dark matter.

“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,” study leader Toby Brown, a PhD candidate at ICRAR, said in a news release. “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.”

Brown likens the process to a massive cosmic street sweeper, driving through the universe stripping away gas.

Previous findings have shown ram-pressure stripping within large galaxy clusters, thought to be located within even bigger dark matter halos. The latest findings — detailed in the journal Monthly Notices of the Royal Astronomical Society – show the phenomenon is present within smaller more isolated collections of galaxies and dark matter.

“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,” Brown said.

Galaxies can be strangled — their gas supply cut off — in a variety of ways, but most are relatively slow processes. Ram-pressure stripping isn’t a slow process.

“On the contrary, what ram-pressure stripping does is bop the galaxy on the head and remove its gas very quickly — of the order of tens of millions of years — and astronomically speaking that’s very fast,” Brown concluded.