Scientists have found evidence that dark matter can be heated and displaced in galaxies as a result of star formation. The results provide the first observable evidence for the effect known as "heating of dark matter" and provide new clues as to what constitutes dark matter. The research was published today in the journal Monthly Notices of the Royal Astronomical Society.
In the new work, scientists from the University of Surrey, Carnegie Mellon University and ETH Zurich are looking for evidence of dark matter in the centers of nearby dwarf galaxies. Dwarf galaxies are small, weak galaxies that normally orbit larger galaxies like our own Milky Way galaxy. They could contain clues that could help us better understand the nature of dark matter.
It is believed that dark matter makes up most of the mass of the universe. However, since it does not interact with light like normal matter, it can only be observed by its gravitational effects. The key to his investigation, however, might be how stars form in these galaxies.
When stars are born, strong winds can force gas and dust from the heart of the galaxy. As a result, the center of the galaxy has less mass, which affects how much gravity is perceived by the remaining dark matter. With less attraction, dark matter gains energy and wanders away from the center, an effect called warming of dark matter.
The team of astrophysicists measured the amount of dark matter in the centers of 16 dwarf galaxies with very different star formation stories. They found that galaxies that stopped forming stars a long time ago had a higher density of dark matter in their centers than those that still form stars today. This supports the theory that the older galaxies warmed up less dark matter.
Professor Justin Read, principal author of the study and head of the Department of Physics of the University of Surrey, said: "We have found a really remarkable relationship between the two amount of dark matter in the centers of these little dwarfs and the amount of star formation that they have experienced in their lives. The dark matter in the centers of the star-forming dwarves seems to have been "heated up" and displaced.
The results represent a new caveat for dark matter models: dark matter must be able to form dwarf galaxies that exhibit a series of central densities, and these densities must relate to the extent of star formation.
Professor Matthew Walker, co-author of Carnegie Mellon University, added, "This study could be proof of the 'smoking weapon' one step closer to understanding dark matter, and our finding that it can be heated and moved motivates the search for particles dark matter. "
The team hopes to expand this work by measuring the central density of dark matter in a larger sample of dwarfs and even amplifying weaker galaxies and testing a wider range of dark matter models.  Publication: JI Read et al.: "Dark matter warms up in dwarf galaxies", MNRAS, 2019; doi: 10.1093 / mnras / sty3404