Researchers at Yale University found that smaller clumps of dark matter are significantly more concentrated than previously thought.
Dark matter is the invisible “glue” that holds stars together within a galaxy, makes up most of the Universe’s mass and provides the necessary support for galaxies to form clusters.
It does not emit, absorb or reflect light, nor does it interact with other known particles, so its presence is only known through its gravitational pull on visible matter.
Dark matter is heaped in regions where galaxy clusters exist. Each of these massive systems, held together by gravity, consists of approximately 1,000 galaxies – each carrying a portion of dark matter.
The new study
In a new study, scientists analyzed images from the Hubble Space Telescope of various clusters of massive galaxies and found that smaller clumps of dark matter are significantly more concentrated than expected.
The research, led by astrophysicist Priyamvada Natarajan, from Yale University, was accepted for publication in the journal Science and will appear in its Sept. 11 issue.
The study results indicate that there is a feature of the Universe that “we are simply not capturing in our current theoretical models,” Natarajan said.
“This could signal a gap in our current understanding of the nature of dark matter and its properties, as this exquisite data has permitted us to probe the detailed distribution of dark matter on the smallest scales.”
Astronomers were able to “map” the distribution of dark matter within galaxy clusters through the curvature of the light produced by them.
They use a technique called gravitational lensing. The higher the concentration of dark matter in a cluster, the more dramatic the observed lensing effect.
In a 3D representation of the data, the scientists observed a “mountain range”, where the peaks indicate clumps of dark matter associated with clusters of individual galaxies.
The team was able to compare the data obtained in the research with computer simulations of galaxy clusters.
They found that the simulations did not show any level of dark matter concentration at smaller scales, different from what they observed in the research.
“To me personally, detecting a gnawing gap — a factor of 10 discrepancy in this case — between an observation and theoretical prediction is very exciting,” Natarajan said. “A key goal of my research has been testing theoretical models with the improving quality of data to find these gaps.”
“It’s these kinds of gaps and anomalies that have often revealed that either we were missing something in the current theory, or it points the way to a brand-new model, which will have more explanatory power.”