New research on the oldest studied dark matter could break the standard cosmological model

A collaborative study has investigated the nature of dark matter surrounding galaxies as they appeared 12 billion years ago, which is billions of years older than the dark matter studied before. The research findings open up the possibility that fundamental cosmological rules may differ when examining the early history of the universe. The findings have been published in Physical Review Letters.

When observing dark matter scientists face a lot of challenges. The biggest is that since dark matter does not emit light, observing it can be a problem. But the mass of the galaxy and the dark matter within it distorts the surrounding space and time, which bends the light that travels through it. Scientists measure the amount of dark matter using this distortion.

But beyond a certain point, scientists encounter a problem. The light from really distant galaxies is incredibly faint. As a result, this technique gets less effective the further away a galaxy. Most previous studies have been unable to analyze the dark matter from more than eight to ten billion years ago. This meant that the distribution of dark matter between this time and when the universe was formed around 13.8 billion years ago was unknown.

The research team led by Hironae Miyatake from Nagoya University used a different source of background light to observe this distortion: the microwaves released from the Big Bang itself. They first used data from the Subaru Hyper Suprime-Cam Survey (HSC) to identify 1.5 million lens galaxies (galaxies that distort the light coming from behind them).

The team then took advantage of the cosmic microwave background (CMB), the residual radiation from the Big Bang. They used microwave observations by the European Space Agency’s Planck satellite to measure how the dark matter around the lens galaxies distorted the microwave radiations that came from the big bang.

The research helped scientists make an exciting discovery related to the “clumpiness” of dark matter. According to the Lambda-CDM model, the Standard Model of Cosmology, CMB fluctuations form “clumps” of densely packed matter that attract surrounding matter through gravity. Even though it is not conclusive, the new research indicates that the measurement was lower than predicted by the Lambda-CDM model.

“Our finding is still uncertain. But if it is true, it would suggest that the entire model is flawed as you go further back in time. This is exciting because if the result holds after the uncertainties are reduced, it could suggest an improvement of the model that may provide insight into the nature of dark matter itself,” said Miyatake, in a press statement. The next step for the research is to use more extensive and sophisticated datasets to allow for a more precise measurement of dark matter distribution.


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