Nav: Home

Taking the temperature of dark matter

January 15, 2020

Warm, cold, just right? Physicists at the University of California, Davis are taking the temperature of dark matter, the mysterious substance that makes up about a quarter of our universe.

We have very little idea of what dark matter is and physicists have yet to detect a dark matter particle. But we do know that the gravity of clumps of dark matter can distort light from distant objects. Chris Fassnacht, a physics professor at UC Davis and colleagues are using this distortion, called gravitational lensing, to learn more about the properties of dark matter.

The standard model for dark matter is that it is 'cold,' meaning that the particles move slowly compared to the speed of light, Fassnacht said. This is also tied to the mass of dark matter particles. The lower the mass of the particle, the 'warmer' it is and the faster it will move.

The model of cold (more massive) dark matter holds at very large scales, Fassnacht said, but doesn't work so well on the scale of individual galaxies. That's led to other models including 'warm' dark matter with lighter, faster-moving particles. 'Hot' dark matter with particles moving close to the speed of light has been ruled out by observations.

Former UC Davis graduate student Jen-Wei Hsueh, Fassnacht and colleagues used gravitational lensing to put a limit on the warmth and therefore the mass of dark matter. They measured the brightness of seven distant gravitationally lensed quasars to look for changes caused by additional intervening blobs of dark matter and used these results to measure the size of these dark matter lenses.

If dark matter particles are lighter, warmer and more rapidly-moving, then they will not form structures below a certain size, Fassnacht said.

"Below a certain size, they would just get smeared out," he said.

The results put a lower limit on the mass of a potential dark matter particle while not ruling out cold dark matter, he said. The team's results represent a major improvement over a previous analysis, from 2002, and are comparable to recent results from a team at UCLA.

Fassnacht hopes to continue adding lensed objects to the survey to improve the statistical accuracy.

"We need to look at about 50 objects to get a good constraint on how warm dark matter can be," he said.
-end-
A paper describing the work is published in the Monthly Notices of the Royal Astronomical Society. Additional coauthors are: W. Enzi, S. Vegetti and G. Despali, Max Planck Institute for Astrophysics, Garching, Germany; M. W. Auger, Institute of Astronomy, University of Cambridge, U.K.; L. V. E. Koopmans, Kapteyn Astronomical Institute, University of Groningen, The Netherlands and J. P. McKean, Netherlands Institute for Radio Astronomy. The work was supported by the National Science Foundation, the Netherlands Organization for Scientific Research and the Chinese Academy of Sciences.

University of California - Davis

Related Dark Matter Articles:

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).
Could the mysteries of antimatter and dark matter be linked?
RIKEN researchers and collaborators have performed the first laboratory experiments to determine whether a slightly different way in which matter and antimatter interact with dark matter might be a key to solving both mysteries.
Placing another piece in the dark matter puzzle
A team led by Prof Dmitry Budker has continued their search for dark matter within the framework of the 'Cosmic Axion Spin Precession Experiment' (or 'CASPEr' for short).
Physicists have found a way to 'hear' dark matter
Physicists at Stockholm University and the Max Planck Institute for Physics have turned to plasmas in a proposal that could revolutionise the search for the elusive dark matter.
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

Climate Mindset
In the past few months, human beings have come together to fight a global threat. This hour, TED speakers explore how our response can be the catalyst to fight another global crisis: climate change. Guests include political strategist Tom Rivett-Carnac, diplomat Christiana Figueres, climate justice activist Xiye Bastida, and writer, illustrator, and artist Oliver Jeffers.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Speedy Beet
There are few musical moments more well-worn than the first four notes of Beethoven's Fifth Symphony. But in this short, we find out that Beethoven might have made a last-ditch effort to keep his music from ever feeling familiar, to keep pushing his listeners to a kind of psychological limit. Big thanks to our Brooklyn Philharmonic musicians: Deborah Buck and Suzy Perelman on violin, Arash Amini on cello, and Ah Ling Neu on viola. And check out The First Four Notes, Matthew Guerrieri's book on Beethoven's Fifth. Support Radiolab today at Radiolab.org/donate.