Nav: Home

Mystery of ultra-diffuse faint galaxies solved

November 28, 2016

Over the last year, researchers have observed some very faint, diffuse galaxies. The galaxies are as faint as dwarf galaxies, but are distributed over an area just as large as the Milky Way.

It has been a mystery, how galaxies so faint - containing up to 1000 times fewer stars than the Milky Way could still be just as large. Now new research from the Niels Bohr Institute shows that if a lot of supernovae explode during the star formation process, it can result in both the stars and the dark matter being pushed outwards, causing the galaxy to expand. The results are published in the scientific journal, Monthly Notices of the Royal Astronomical Society, Oxford University Press.

Galaxies are gigantic collections of stars, gas and so-called dark matter. The smallest galaxies contain a few million stars, while the largest may contain several hundred billion stars. The first stars already emerged in the very early universe about 200 million years after the Big Bang, formed from the gases hydrogen and helium. These giant clouds of gas and dust contract and eventually the gas is so compact that that the pressure heats up the material, creating glowing balls of gas and new stars are born. The stars are collected into galaxies, the first of which were baby galaxies of a sort.

The theory of the astronomers is that the baby galaxies gradually grew larger and more massive by constantly forming new stars and by colliding with neighbouring galaxies to form new, larger galaxies. The largest galaxies in our current universe have thus been under constant formation throughout the history of the universe. Earth and our solar system are located in a large galaxy, the Milky Way.

But the newly discovered, ultra-diffuse faint galaxies were difficult to classify and while some researchers thought that diffuse galaxies were just large spiral galaxies with a large amount of dark matter, others thought that it was a case of ordinary dwarf galaxies.

Recreating galaxies

But a research project led by a researcher from the Niels Bohr Institute at the University of Copenhagen has been able to recreate the characteristics of the galaxies that have been observed by using advanced computer simulations, performed in collaboration with the New York University Abu Dhabi.

"By recreating almost 100 virtual galaxies, we have shown that when there are a lot of supernovae during the star formation process, it can result in the stars and the dark matter in the galaxy to be pushed outwards, causing the extent of the galaxy to expand. When there is a small number of stars in an expanded area, it means that the galaxy becomes faint and diffuse and is therefore difficult to observe with telescopes," explains Arianna Di Cintio, PhD in astrophysics, Dark Cosmology Centre at the Niels Bohr Institute at the University of Copenhagen, who is the leading researcher of the project.

She explains that the mechanism that causes the stars to move away from the centre is the same one that is able to create areas with a lower density of dark matter. The many supernovae are so powerful that they blow the gas outwards in the galaxy. As a result both the dark matter and the stars move outwards so that the extent of the galaxy expands. The fact that the galaxy is spread over a larger area means that it becomes more diffuse and unclear.

"If we can recreate ultra-diffuse galaxies with computer simulations, it proves that we are on track with our cosmological model. We therefore predict that there are ultra-diffuse galaxies everywhere - not only in galaxy clusters. They are dominated by dark matter and only a small percentage of their content is comprised of gas and stars and the most important thing is that they are dwarf galaxies with a mass of only about 10 to 60 times less than a large spiral galaxy, which is to say significantly smaller than a large galaxy like the Milky Way," says Arianna Di Cintio.

In addition, the researchers expect that among the more isolated located ultra-diffuse galaxies, the largest could contain more gas. They are therefore initiating close collaborations with research groups carrying out observations of very distant areas of the sky with powerful telescopes in order to confirm these theories.

"It will open a whole new window into galaxy formation - there may be thousands of ultra-faint galaxies that are just waiting to be discovered," says Arianna Di Cintio, who is looking forward to finding out their amount of stars, their content of elements and how the ultra-diffuse galaxies survive in galaxy clusters.
-end-
Contact:

Arianna Di Cintio. DARK Carlsberg fellow, Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, arianna.dicintio@dark-cosmology.dk, +45 5366-5372

University of Copenhagen - Niels Bohr Institute

Related Dark Matter Articles:

Holding up a mirror to a dark matter discrepancy
The universe's funhouse mirrors are revealing a difference between how dark matter behaves in theory and how it appears to act in reality.
Zooming in on dark matter
Cosmologists have zoomed in on the smallest clumps of dark matter in a virtual universe - which could help us to find the real thing in space.
Looking for dark matter with the universe's coldest material
A study in PRL reports on how researchers at ICFO have built a spinor BEC comagnetometer, an instrument for studying the axion, a hypothetical particle that may explain the mystery of dark matter.
Looking for dark matter
Dark matter is thought to exist as 'clumps' of tiny particles that pass through the earth, temporarily perturbing some fundamental constants.
New technique looks for dark matter traces in dark places
A new study by scientists at Lawrence Berkeley National Laboratory, UC Berkeley, and the University of Michigan -- published today in the journal Science - concludes that a possible dark matter-related explanation for a mysterious light signature in space is largely ruled out.
Researchers look for dark matter close to home
Eighty-five percent of the universe is composed of dark matter, but we don't know what, exactly, it is.
Galaxy formation simulated without dark matter
For the first time, researchers from the universities of Bonn and Strasbourg have simulated the formation of galaxies in a universe without dark matter.
Taking the temperature of dark matter
Warm, cold, just right? Physicists at UC Davis are using gravitational lensing to take the temperature of dark matter, the mysterious substance that makes up about a quarter of our universe.
New clues on dark matter from the darkest galaxies
Low-surface-brightness (LSB) galaxies offered important confirmations and new information on one of the largest mysteries of the cosmos: dark matter.
A new approach to the hunt for dark matter
A study that takes a novel approach to the search for dark matter has been performed by the BASE Collaboration at CERN working together with a team at the PRISMA+ Cluster of Excellence at Johannes Gutenberg University Mainz (JGU).
More Dark Matter News and Dark Matter Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: The Power Of Spaces
How do spaces shape the human experience? In what ways do our rooms, homes, and buildings give us meaning and purpose? This hour, TED speakers explore the power of the spaces we make and inhabit. Guests include architect Michael Murphy, musician David Byrne, artist Es Devlin, and architect Siamak Hariri.
Now Playing: Science for the People

#576 Science Communication in Creative Places
When you think of science communication, you might think of TED talks or museum talks or video talks, or... people giving lectures. It's a lot of people talking. But there's more to sci comm than that. This week host Bethany Brookshire talks to three people who have looked at science communication in places you might not expect it. We'll speak with Mauna Dasari, a graduate student at Notre Dame, about making mammals into a March Madness match. We'll talk with Sarah Garner, director of the Pathologists Assistant Program at Tulane University School of Medicine, who takes pathology instruction out of...
Now Playing: Radiolab

What If?
There's plenty of speculation about what Donald Trump might do in the wake of the election. Would he dispute the results if he loses? Would he simply refuse to leave office, or even try to use the military to maintain control? Last summer, Rosa Brooks got together a team of experts and political operatives from both sides of the aisle to ask a slightly different question. Rather than arguing about whether he'd do those things, they dug into what exactly would happen if he did. Part war game part choose your own adventure, Rosa's Transition Integrity Project doesn't give us any predictions, and it isn't a referendum on Trump. Instead, it's a deeply illuminating stress test on our laws, our institutions, and on the commitment to democracy written into the constitution. This episode was reported by Bethel Habte, with help from Tracie Hunte, and produced by Bethel Habte. Jeremy Bloom provided original music. Support Radiolab by becoming a member today at Radiolab.org/donate.     You can read The Transition Integrity Project's report here.