Observations may hint at nature of dark matter
Using the NASA/ESA Hubble Space Telescope, astronomers have discovered that the brightest galaxies within galaxy clusters "wobble" relative to the cluster's centre of mass. This unexpected result is inconsistent with predictions made by the current standard model of dark matter. With further analysis it may provide insights into the nature of dark matter, perhaps even indicating that new physics is at work.
Abell S1063, a galaxy cluster, was observed by the NASA/ESA Hubble Space Telescope as part of the Frontier Fields programme. The huge mass of the cluster acts as a cosmic magnifying glass and enlarges even more distant galaxies, so they become bright enough for Hubble to see.
Credit: NASA, ESA, and J. Lotz (STScI)
Dark matter constitutes just over 25 percent of all matter in the Universe but cannot be directly observed, making it one of the biggest mysteries in modern astronomy. Invisible halos of elusive dark matter enclose galaxies and galaxy clusters alike. The latter are massive groupings of up to a thousand galaxies immersed in hot intergalactic gas. Such clusters have very dense cores, each containing a massive galaxy called the "brightest cluster galaxy" (BCG).
The standard model of dark matter (cold dark matter model) predicts that once a galaxy cluster has returned to a "relaxed" state after experiencing the turbulence of a merging event, the BCG does not move from the cluster's centre. It is held in place by the enormous gravitational influence of dark matter.
But now, a team of Swiss, French, and British astronomers have analysed ten galaxy clusters observed with the NASA/ESA Hubble Space Telescope, and found that their BCGs are not fixed at the centre as expected .
The Hubble data indicate that they are "wobbling" around the centre of mass of each cluster long after the galaxy cluster has returned to a relaxed state following a merger. In other words, the centre of the visible parts of each galaxy cluster and the centre of the total mass of the cluster -- including its dark matter halo -- are offset, by as much as 40 000 light-years.
"We found that the BCGs wobble around centre of the halos," explains David Harvey, astronomer at EPFL, Switzerland, and lead author of the paper. "This indicates that, rather than a dense region in the centre of the galaxy cluster, as predicted by the cold dark matter model, there is a much shallower central density. This is a striking signal of exotic forms of dark matter right at the heart of galaxy clusters."
The wobbling of the BCGs could only be analysed as the galaxy clusters studied also act as gravitational lenses. They are so massive that they warp spacetime enough to distort light from more distant objects behind them. This effect, called strong gravitational lensing, can be used to make a map of the dark matter associated with the cluster, enabling astronomers to work out the exact position of the centre of mass and then measure the offset of the BCG from this centre.
If this "wobbling" is not an unknown astrophysical phenomenon and in fact the result of the behaviour of dark matter, then it is inconsistent with the standard model of dark matter and can only be explained if dark matter particles can interact with each other -- a strong contradiction to the current understanding of dark matter. This may indicate that new fundamental physics is required to solve the mystery of dark matter.
Co-author Frederic Courbin, also at EPFL, concludes: "We're looking forward to larger surveys -- such as the Euclid survey -- that will extend our dataset. Then we can determine whether the wobbling of BGCs is the result of a novel astrophysical phenomenon or new fundamental physics. Both of which would be exciting!"
The Hubble Space Telescope is a project of international cooperation between ESA and NASA.
This research was presented in a paper entitled "A detection of wobbling Brightest Cluster Galaxies within massive galaxy clusters" by Harvey et al., which appeared in the Monthly Notices of the Royal Astronomical Society.
The international team of astronomers in this study consists of David Harvey (Laboratoire d'Astrophysique EPFL, Switzerland), F. Courbin (Laboratoire d'Astrophysique EPFL, Switzerland), J.P. Kneib (Laboratoire d'Astrophysique EPFL, Switzerland; CNRS, France), and Ian G. McCarthy (Liverpool John Moores University, UK).
Image credit: NASA, ESA, J. Lotz (STScI), M. Postman (STScI), J. Richard (CRAL) and J.-P. Kneib (LAM), T. Lauer (NOAO), S. Perlmutter (UC Berkeley, LBNL), A. Koekemoer (STScI), A. Riess (STScI/JHU), J. Nordin (LBNL, UC Berkeley), D. Rubin (Florida State), C. McCully (Rutgers University) and the CLASH Team
Laboratoire d'Astrophysique EPFL
Laboratoire d'Astrophysique EPFL
Laboratoire d'Astrophysique - EPFL
ESA/Hubble Public Information Officer
Garching bei München, Germany
Mathias Jäger, ESA/Hubble Public | EurekAlert!
Writing and deleting magnets with lasers
19.04.2018 | Helmholtz-Zentrum Dresden-Rossendorf
Ultrafast electron oscillation and dephasing monitored by attosecond light source
19.04.2018 | Yokohama National University
Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.
Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...
Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.
The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...
Stable joint cartilage can be produced from adult stem cells originating from bone marrow. This is made possible by inducing specific molecular processes occurring during embryonic cartilage formation, as researchers from the University and University Hospital of Basel report in the scientific journal PNAS.
Certain mesenchymal stem/stromal cells from the bone marrow of adults are considered extremely promising for skeletal tissue regeneration. These adult stem...
In the fight against cancer, scientists are developing new drugs to hit tumor cells at so far unused weak points. Such a “sore spot” is the protein complex...
In an article that appears in the journal “Review of Modern Physics”, researchers at the Laboratory for Attosecond Physics (LAP) assess the current state of the field of ultrafast physics and consider its implications for future technologies.
Physicists can now control light in both time and space with hitherto unimagined precision. This is particularly true for the ability to generate ultrashort...
13.04.2018 | Event News
12.04.2018 | Event News
09.04.2018 | Event News
19.04.2018 | Materials Sciences
19.04.2018 | Physics and Astronomy
19.04.2018 | Physics and Astronomy