Kavli Institute for the Physics and Mathematics of the Universe | 2019 Feb 27
Dark matter may scatter against each other only when they hit the right energy, say researchers in Japan, Germany, and Austria in a new study. Their idea helps explain why galaxies from the smallest to the biggest have the shapes they do.Astronomers observed that the dark matter does not seem to clump very much in
small galaxies, but their density peaks sharply in bigger systems such as clusters
of galaxies. It has been a puzzle why different systems behave differently.
(Credit: Kavli IPMU, NASA, STScI)
Dark matter is a mysterious and unknown form of matter that comprises more than 80 per cent of matter in the Universe today. Its nature is unknown, but it is believed to be responsible for forming stars and galaxies by its gravitational pull, which led to our existence. ...
Astronomers have already found dark matter does not seem to clump together as much as computer simulations suggest. If gravity is the only force that drives dark matter, only pulling and never pushing, then dark matter should become very dense towards the center of galaxies. However, especially in small faint galaxies called dwarf spheroidals, dark matter does not seem to become as dense as expected toward their centers.
This puzzle could be solved if dark matter scatters with each other like billiard balls, allowing them to spread out more evenly after a collision.
But one problem with this idea is that dark matter does seem to clump in bigger systems such as clusters of galaxies. What makes dark matter behave differently between dwarf spheroidals and clusters of galaxies? An international team of researchers has developed an explanation that could solve this riddle, and reveal what dark matter is. ...
Velocity Dependence from Resonant Self-Interacting Dark Matter ~ Xiaoyong Chu, Camilo Garcia-Cely, Hitoshi Murayama
- Physical Review Letters 122(07):1103 (22 Feb 2019) DOI: 10.1103/PhysRevLett.122.071103
- arXiv.org > hep-ph > arXiv:1810.04709 > 10 Oct 2018 (v1), 24 Feb 2019 (v2)