Spiral galaxy NGC 4921
This
artist’s impression shows the spiral galaxy NGC 4921 based on
observations made by the Hubble Space Telescope.
Credit: ICRAR, NASA, ESA, the Hubble Heritage Team (STScI/AURA).
Credit: ICRAR, NASA, ESA, the Hubble Heritage Team (STScI/AURA).
An artist’s impression of
ram-pressure stripping of galaxy NGC 4921. Stripping removes gas—the raw
fuel for star formation—and could be the dominant way galaxies are
killed by their environment. Credit: ICRAR, NASA, ESA, the Hubble
Heritage Team (STScI/AURA).
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)
Ram Stripping of Galaxies
An animation showing how ram-pressure stripping removes gas from galaxies, sending them to an early death.
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)
It’s the big astrophysical whodunnit. 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.
Toby Brown, leader of the study and PhD candidate at ICRAR and
Swinburne University of Technology, 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,” 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.
“You can think of it like a giant cosmic broom that comes through and physically sweeps the gas from the galaxies.”
Mr 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.”
ICRAR researcher Dr Barbara Catinella, co-author of the study, said
astronomers already knew ram-pressure stripping affected galaxies in
clusters, which are the most massive halos found in the Universe.
“This paper demonstrates that the same process is operating in much
smaller groups of just a few galaxies together with much less dark
matter,” said Mr. Brown. “Most galaxies in the Universe live in these
groups of between two and a hundred galaxies,” he said.
“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 was published in the journal Monthly Notices of the Royal
Astronomical Society. It 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.
Mr 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,” he said.
“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.”
Publications Details
‘Cold gas stripping in satellite galaxies: from pairs to clusters’,
published in the Monthly Notices of the Royal Astronomical Society on
January 17th, 2017.
Click here for the research paper
More Information
ICRAR
The International Centre for Radio Astronomy Research (ICRAR) is a
joint venture between Curtin University and The University of Western
Australia with support and funding from the State Government of Western
Australia.
Contact Information
Mr Toby Brown (ICRAR-UWA, Swinburne University of Technology)
Email: toby.brown@icrar.org
M: +61 6488 7753
Dr Barbara Catinella (ICRAR-UWA)
Email: barbara.catinella@icrar.org
Tel: +972 89346511
Pete Wheeler—Media Contact, ICRAR
Email: pete.wheeler@icrar.org
M: +61 423 982 018
