The results observed with the telescope show that there are many small gravitational lenses in the galaxy cluster, which are ten times larger than the simulation results. Therefore, something went wrong: either the simulation method or the standard cosmological assumption about the dark matter that produced this phenomenon.
Just like a giant magnifying glass in space, Gravitational lens They are formed by very large objects (such as galaxies or star clusters) that bend the light of other distant objects behind them so that they can be studied. The huge gravitational force that causes matter, especially dark matter, is the cause of the distortion of light in the distance.
my own Galaxy cluster Is a large gravity lens, but galaxy The interior can also be used as a smaller scale lens.
The latter is the result of an analysis conducted by an international team of scientists led by an international research team. National Institute of Astrophysics (INAF) In Italy, they found that the galactic clusters contained more tiny gravitational lenses than standard cosmology expected.The results are published in the journal science.
The author analyzed 11 star clusters and compared the observation results of the small gravitational lens captured by the space telescope. Hubble (NASA/ESA) and Very Large Telescope (VLT) The European Southern Observatory (ESO) in Chile, Computational simulation Regarding the question of how dark matter should be distributed in these galaxy clusters.
The lead author explained to SINC: “Therefore, we found that the ability of real galaxy clusters to produce powerful small-scale lens effects is ten times that of simulations.” Massimo Meneghetti, INAF.
He added: “This shows that the matter in the galaxy has a more compact spatial distribution than theoretically expected.” In other words, the mass density reaching the center of the Milky Way is so high that many of them can produce powerful Lens effect, which will not appear in numerical simulations with the same frequency.
Two possible explanations
In view of these results, the researchers concluded that the standard simulation method must have unknown problems, otherwise cosmologists have made wrong assumptions about the properties of dark matter.
Menegetti admitted: “It is difficult to know which of these two options is more likely.” On the one hand, the physical processes that determine the behavior of ordinary matter in the Milky Way and the interaction with dark matter are very complicated. This is why it is difficult to simulate them-they have a high computational cost and may not be fully understood. Some important ingredients may be lost”.
“But, on the other hand,” he continued, “The currently accepted hypothesis is that dark matter is composed of large particles that do not collide and interact only by gravity. This hypothesis has been affected by the theory and other observations in nearby areas The challenge of difference. Our own galaxy. In addition, these particles have not been detected experimentally, and many other candidates have not been eliminated through observation.
In order to find the answer, the researchers will continue to use different dark matter models to conduct simulations, evaluate whether other candidate dark matter can explain their observations, and extend their analysis to a larger number of gravitationally lensed galaxy clusters.
“For example, in the next few years, Euclid’s mission The ESA team, in which several members of our team are involved, will begin to observe 15,000 square meters of sky, providing observations of thousands of galaxy clusters. “The mystery of the small gravitational lens.
Massimo Meneghetti et al. “Too many small gravitational lenses have been observed in the Milky Way cluster.” science 369, September 2020.