New studies revealed that the so-called ram-pressure stripping phenomenon is more prevalent than previously thought and it is killing entire galaxies.
A global team of researchers, based at the International Centre for Radio Astronomy Research (ICRAR), led by the astronomer Toby Brown, studied about 11,000 galaxies and found out that their gas (the lifeblood for star formation) is being violently stripped away on a widespread scale throughout the local Universe.
Brown said removing the gas from galaxies leaves them unable to form new stars. “It dictates the life of the galaxy because the existing stars will cool off and grow old,” he said. “If you remove the fuel for star formation then you effectively kill the galaxy and turn it into a dead object.”
An artist’s impression showing the increasing effect of ram-pressure stripping in removing gas from galaxies, sending them to an early death. Credit: ICRAR, NASA, ESA, the Hubble Heritage Team (STScI/AURA)
The leader of the study also said the image we paint as astronomers is that galaxies are embedded in clouds of dark matter that we call dark matter halos.
Dark matter is the mysterious material that despite being invisible accounts for roughly 27 per cent of our Universe, while ordinary matter makes up just 5 per cent. The remaining 68 per cent 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,” Brown said.
He also explains: “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.”
“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”, he complements.
“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.”
Animation: Ram Pressure Stripping of Galaxies
An animation showing how ram-pressure stripping removes gas from galaxies, sending them to an early death. Credit: ICRAR, NASA, ESA, the Hubble Heritage Team (STScI/AURA)