Dark matter halo magnification

Dark matter halo magnification

The artist’s impression of a dark matter halo of varying mass in space. Source: YU Jingchuan, Beijing Planetarium

Most of the matter in the universe is dark and is essentially completely different from the material that makes up stars, planets, and man. Galaxies form and grow as gases cool and condense in the center of this massive mass of dark matter, the so-called dark matter halo.

An international research team, led by Professor Wang Ji of the National Astronomical Observatories of the Chinese Academy of Sciences (NAOC), uses Chinese and European supercomputers to expand the typical realm of a virtual universe, as if it were fleas on the surface of the moon. Can be seen.

This study is nature On September 2, 2020.

Today, the largest dark matter halo in the universe is home to a massive cluster of galaxies, with hundreds of bright galaxies. The properties of such clusters, which are a thousand trillion (million billion) times as large as our Sun, are well studied.

On the other hand, the mass of the smallest dark matter halo is unknown. According to the current popular theory, they hypothesized about the mass of the Earth.

Such little halos will be very numerous, containing a significant portion of all dark matter in the universe. However, stars and galaxies will remain dark throughout cosmic history because they only grow in halos that are a million times heavier than the sun.

“This little halo can only be studied by simulating the evolution of the universe on a large supercomputer,” said Professor WANG.

Projected dark matter density

Simulations of the formation of dark matter halos of varying sizes from Earth’s mass to galaxy clusters allow us to find universal halo-density structures with masses of up to 20 orders of magnitude. Source: Harvard University Astrophysics Center, Ph.D. Sownak Bose

Research teams based on the National Observatory of the Chinese Academy of Sciences in China, the University of Durham in the UK, the Max Planck Institute for Astrophysics in Germany, and the Center for Astrophysics in the United States conduct development, testing and space zoom.

This allowed them to study the structure of dark matter halos of all masses between Earth and large galaxy clusters. In terms of numbers, the zoom covers a mass range from 10 to a power of 30 (i.e. 30 with 1 followed by 0), which corresponds to the number of kilograms in the sun.

Magnifying the virtual universe with these fine details allowed researchers to study the structure of dark matter halos ranging from Earth’s mass to large clusters of galaxies.

“Surprisingly, halos of all sizes have a very similar internal structure. In other words, it’s very dense in the center and spreads out more and has little chunks orbiting the outer area,” Professor WANG said. “Without a measurement scale, it was almost impossible to describe an image of the dark matter halo of a massive galaxy in a galaxy whose mass is part of the sun.”

Particles of dark matter can collide near the center of the halo and, according to some theories, can be dissipated by an explosion of energy (gamma) radiation.

“By magnifying this relatively small dark matter halo, we can calculate the amount of radiation expected to come out of different sized halos,” said co-author Professor Carlos Frenk of Durham University.

Most of this radiation will be emitted by dark matter halos that are too small to contain stars, and future gamma-ray observatories can detect these emissions and “visible” these small objects individually or collectively.

Simon White, co-author of the Max Planck Institute for Astrophysics, said, “This will eventually confirm the hypothesized properties of dark matter, which may not be completely dark. “Our research sheds light on this little halo as we try to learn more about what dark matter is and its role in the evolution of the universe.”

Read Zooming In Tight on Dark Matter to learn more about this research.

References: J. Wang, S. Bose, CS Frenk, L. Gao, A. Jenkins, V. Springel and SDM White, September 2, 2020, “Universal Structures of Dark Matter Halo of Twenty Times or More”, nature.
DOI:10.1038 / s41586-020-2642-9

Simulations were performed on cosmology mechanical supercomputers in Guangzhou, China, Durham, England, and Munich, Germany.

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