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Dark Matter Heats Up Then Moves Away During Star Formation In Dwarf Galaxies

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A new study found that dark matter can heat up and then move away from the center of galaxies. This phenomenon called dark matter heating is typical of any star-forming galaxy.  ( University of Surrey )

Astrophysicists find a new piece of evidence showing that dark matter moves heats up and then moves away during the process of star formation.

It is a long-held theory that the universe is largely made up of dark matter. Dark matter does not interact directly with light, which is why scientists can only study them with respect to their gravitational effect. This new finding published in the journal Monthly Notices of the Royal Astronomical Society provides a deeper understanding of the behavior of dark matter.

Dark Matter Heating

Scientists from the University of Surrey in UK, Carnegie Mellon University, and ETH Zürich in Switzerland studied 16 dwarf galaxies in search for traces of dark matter. Dwarf galaxies are smaller and faint galaxies that orbit larger ones like the Milky Way.

During the formation of stars, gas and dust are pushed away from the core of the galaxy. With less mass, dark matter gains more energy and then move away from the center in a process called dark matter heating.

"We found a truly remarkable relationship between the amount of dark matter at the centers of these tiny dwarfs, and the amount of star formation they have experienced over their lives. The dark matter at the centers of the star-forming dwarfs appears to have been 'heated up' and pushed out," said Justin Read, the lead author of the study and professor of the Department of Physics at the University of Surrey.

Results of their study also coincided with an earlier notion that galaxies that have stopped forming stars long ago have higher dark matter densities and therefore, less dark matter heating.

"Our results suggest that, to leading order, dark matter is a cold, collisionless, fluid that can be kinematically 'heated up' and moved around," the authors wrote in their study.

Origin Of Dark Matter

In a related study, astronomer Alfred Tiley and his team from Durham University surveyed 1,500 star-forming galaxies in an effort to determine the origin of dark matter. The researchers calculated the galaxies' rotation rates by combining the light of faint galaxies in distance.
The researchers concluded that the amount of dark matter that existed in old galaxies is nearly the same as the dark matter present among fairly young galaxies.

Tiley's theory was contradicted by Reinhard Genzel, an astronomer at the Max Planck Institute for Extraterrestrial Physics in Germany. Genzel said that the new study used only one approach that represented largely the low-mass galaxies that existed in the early ages of the universe.

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