Scientists have found that dark matter can be heated and set in motion as stars form in galaxies. This study for the first time observationally confirms the effect known as "heating of dark matter", and provides new clues to understanding this mysterious substance.
In this new work, scientists led by Justin Read from the University of Surrey, UK, set out to find evidence of the presence of dark matter in the centers of nearby dwarf galaxies. Dwarf galaxies are small, faint galaxies that usually orbit larger galaxies like the Milky Way. Studying dwarf galaxies could provide clues to understanding dark matter.
Dark matter supposedly makes up most of the mass in the universe. However, since it does not interact with light in the same way as normal matter, the presence of dark matter is revealed only by its gravitational effects. The key to studying it, however, may lie in the formation of stars in galaxies.
When new stars form in the galaxy, powerful stellar winds can push gas and dust away from the center of the galaxy. As a result, less mass remains at the center of the galaxy, and the gravitational effect on dark matter in that galaxy is reduced. As a result of the weakening of gravitational attraction, dark matter receives additional energy and migrates away from the center of the galaxy - an effect called "heating up dark matter."
Reed's team measured the amount of dark matter in the centers of 16 dwarf galaxies with different star formation histories. The analysis showed that galaxies in which star formation stopped a long time ago have a higher density of dark matter in their centers, compared to galaxies in which star formation is still taking place. These observations support the hypothesis that there is almost no heating of dark matter in older galaxies, the authors say.
The research is published in the Monthly Notices of the Royal Astronomical Society.