Small-scale fluctuations discovered in the dark matter of the Universe

materia oscura

Groundbreaking study used ALMA to pave the way to a deeper understanding of the true nature of dark matter

ALMA/DICYT A research team led by Professor Kaiki Taro Inoue from Kindai University in Osaka, Japan, used the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile to make an unprecedented discovery. The team has discovered fluctuations in the distribution of dark matter in the Universe on a scale smaller than that of massive galaxies.


Esta es la primera vez que se detectan fluctuaciones espaciales de la materia oscura en el Universo lejano en escalas inferiores a 30.000 años luz. Este resultado muestra que la materia oscura fría 1 se ve favorecida incluso en escalas más pequeñas que las galaxias masivas y es un paso esencial hacia la comprensión de la verdadera naturaleza de la materia oscura. El artículo se publicó en “The Astrophysical Journal” el 7 de septiembre.

Small-scale fluctuations in the dark matter of the Universe./ALMA.

Dark matter, the invisible material that makes up a significant fraction of the mass of the Universe, is believed to have played an important role in the formation of structures such as stars and galaxies 2. Since dark matter is not distributed uniformly in space but in groups, their gravity can slightly change the path of light (including radio waves) from distant light sources. Observations of this effect (gravitational lensing) have shown that dark matter is associated with relatively massive galaxies and galaxy clusters. However, how it is distributed at smaller scales is unknown.


Using ALMA's exceptional observation power, the research team focused on a distant quasar 3, MG J0414+0534 4, located 11 billion light years from Earth. This particular quasar displays a rare quad image thanks to the gravitational lensing effects of a foreground galaxy. However, the positions and shapes of these images did not match calculations based solely on the gravitational pull of the foreground galaxy, indicating another influence at play.


Further investigation revealed the source of this discrepancy: the effects of dark matter on a scale smaller than that of large galaxies, specifically, less than 30,000 light-years away. These findings confirmed and enriched the theoretical model of cold dark matter. According to theory, these dark matter clumps are distributed not only within galaxies but also in intergalactic spaces.


The challenge lies in the fact that gravitational lensing effects induced by these small clumps of dark matter are difficult to detect on their own. However, ALMA's high-resolution capabilities, along with the lensing effect of the foreground galaxy, enabled this pioneering detection. Therefore, this research is an important step towards verifying dark matter theories and further unraveling its enigmatic nature.

Octavio Alonso