Weird dark matter waves seem to warp the light from distant galaxies

There is growing evidence of ultralight dark matter particles called axions. Studies of galaxy-distorted light show that it is better explained by axion dark matter than weakly interacting massive particles (WIMPs), the leading candidates for dark matter.

Researchers are fairly certain that dark matter exists because of its gravitational effects, but so far all efforts to directly detect dark matter particles have failed.Amruth Alfred of the University of Hong Kong and his colleagues took another indirect look at dark matter by looking at an effect called gravitational lensing. This is where light from distant objects is distorted and magnified by the gravitational fields of relatively nearby galaxies, creating multiple images of background objects around nearby galaxies called Einstein rings.

Since galaxies are expected to be surrounded by halos of dark matter, the properties of that dark matter should affect how light is stretched. Axions are many orders of magnitude less massive than her WIMPs, so we would expect them to behave differently. A WIMP behaves like a standard particle, but an axion is so light that it should behave like a wave due to quantum effects.

Therefore, if the foreground galaxy is surrounded by axions due to gravitational lensing, it is expected to affect how the image looks after the background galaxy undergoes the lensing effect. “You can put a stone in a pool with waves and when you look at the stone you can see the waves vibrating,” said Razieh Emami of the Harvard-Smithsonian Center for Astrophysics in Massachusetts, USA. I’m here. was part of the research team. “In these observations, these wave structures translate directly into the position of the lens image and its brightness.”

Although we know there are anomalies between gravitational lensing and the patterns seen in the WIMP model, the researchers found that switching the WIMP model to the axion model eliminated these anomalies. We also tested the model on a real lens system and found that the axion model fits much better.

“Since dark matter only interacts through gravity (and possibly weak forces in some models), this is one of the purer tests that can be performed to investigate the nature of dark matter,” says Alfred. say. “Wave-like dark matter … withstands the scrutiny we put it under.”

This is good news for Axion, which has been overshadowed by WIMP as a dark matter candidate for decades. “Gravitational lensing tilts the scale from heavier to lighter particles,” says Emami. “So far, there are no other explanations for this phenomenon.”

“I don’t think this is proof that ultralight axions exist, but it is a compelling result,” said Chanda Prescod-Weinstein of the University of New Hampshire. “It provides further evidence that axions are an attractive class of dark matter candidates.”

A great deal of effort has gone into detecting WIMPs, but due to bad luck, this research is part of a renaissance of axions and other dark matter candidates that have not been fully explored. “Axion represents one of the simplest extensions of the standard model of particle physics, and much of its plausible search space remains unexplored,” said Harvard-Smithsonian Astrophysics. Belongs to the academic center and works. “In other words, we are waiting for results that are easily achievable compared to what has been done for other candidates like WIMPs.”