The Milky Way’s Destiny? –“Dark Matter Clouds are Killing Galaxies Throughout the Cosmos” (VIDEO)


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Through the cosmos, galaxies are dying off, and the question astronomers want answered is, "what's killing them?" New research by a global team of researchers, based at the International Centre for Radio Astronomy Research (ICRAR), has revealed that a 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.

"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," said Toby Brown, leader of the study and PhD candidate at ICRAR and Swinburne University of Technology. "The image we paint as astronomers is that galaxies are embedded in invisible clouds of dark matter that we call dark matter halos. 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."

 The image above is The Aquarius Project simulation of a Milky Way-size dark matter halo. (Volker Springel, Max Planck Institute for Astrophysics).

High resolution cosmological N-body simulation, Cosmogrid, shown below lets you follow the formation and evolution of a lot of Milky Way like dark matter halos. This movie focuses on the largest dark matter halos at z=0 (current Univese). This simulation was partially carried on Cray XT4 at Center for Computational Astrophysics, CfCA, of National Astronomical Observatory of Japan. (Tomoaki Ishiyama, University of Tsukuba)



Brown said the other main process by which galaxies run out of gas and die is known as strangulation.
"Strangulation occurs when the gas is consumed to make stars faster than it's being replenished, so the galaxy starves to death. It's a slow-acting 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."



An artist's impression above shows 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)

"You can think of it like a giant cosmic broom that comes through and physically sweeps the gas from the galaxies," 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. f you remove the fuel for star formation then you effectively kill the galaxy and turn it into a dead object."

"Most galaxies in the Universe live in these groups of between two and a hundred galaxies," he added.

"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."

The study, published in the journal Monthly Notices of the Royal Astronomical Society, used an innovative technique combining the largest optical galaxy survey ever completed—the Sloan Digital Sky Survey—with the largest set of radio observations for atomic gas in galaxies —the Arecibo Legacy Fast ALFA survey.

The Daily Galaxy via International Centre for Radio Astronomy Research


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