Intergalactic bridges made of dark matter

A new map of dark matter in the local universe reveals several previously unknown filament structures that connect galaxies together. The map was developed by an international team from Pennsylvania State University, and the map could enable studies of the nature of dark matter as well as the history and future of our local universe.

Dark matter is elusive matter that makes up 85% of the matter in the universe and represents the skeleton of what cosmologists call the “cosmic web”, which is the large structure of the universe which, due to its gravitational effect, determines the movement of galaxies. However, the local dark matter distribution is currently unknown because it cannot be measured directly. Instead, researchers must deduce its distribution based on the effect of gravity on other objects in the universe, such as galaxies.

“Ironically, it is easier to study the distribution of dark matter much further away because it reflects a past so far away, which is much less complex,” he said. Donghui Jeong, Associate Professor of Astronomy and Astrophysics at Pennsylvania and co-author of the study. “Over time, as the large-scale structure of the universe grew, the complexity of the universe increased, so it is inherently difficult to measure dark matter locally.”

Previous attempts to map the cosmic web began with a model of the early universe and then simulate the model’s evolution over billions of years. However, this has not yet been able to provide results detailed enough to see the local universe as well. In the new study, the researchers took a completely different approach, using computer machine learning to build a model that uses information about the distribution and movement of galaxies to predict the distribution of dark matter.

The researchers built and trained their model using a large set of galaxy simulations, called the Illustris-TNG, that includes galaxies, gas, other visible materials and dark matter. The team specifically selected simulation galaxies similar to those in the Milky Way, and finally determined the galaxy properties needed to predict the distribution of dark matter.

The research team then applied their model to real, local universe data from the Cosmicflow-3 galaxy catalog. The catalog contains comprehensive data on the distribution and movement of more than 17,000 galaxies in the vicinity of the Milky Way, within 200 mega-parsecs. The map generated by the global local network is now being published online at http://www.un.org/The Astrophysical Journal.

The map later reproduced the prominent structures known in the local universe, including the “local plate”, a region of space that contains the Milky Way, neighboring galaxies in the “Local Group”, galaxies in the Virgo Cluster, and “local void”. A relatively empty area next to the Local Group. In addition, it has identified several new structures that require further research, including smaller filament structures that connect galaxies.

“Having a local map of the cosmic web opens a new chapter in cosmic study,” Jeong said. We can study how the dark matter distribution relates to other emission data, which will help us understand the nature of dark matter. We can directly study these filamentous structures, these hidden bridges between galaxies. ”

“Since dark matter dominates the dynamics of the universe, it basically determines our destiny,” Jeong said. “So we can ask a computer to develop a map for billions of years to see what will happen in the local universe. And we can develop the model in time to understand the history of our cosmic neighborhood.”