Normal Matter Dominates Dark Matter In Early Galaxies

A new study finds that normal matter dominates the dark matter in early galaxies. This means that dark matter was smaller or minor in the early Universe than today.

The findings were published in the journal Nature on March 16, 2017. The study was led by Reinhard Genzel at the Max Planck Institute for Extraterrestrial Physics in Garching, Germany, and other colleagues. The study could aid the scientists in understanding how galaxies and the "haloes" of dark matter altered over time, according to Space.com.

The normal matter includes the shining stars, clouds of dust and glowing gas. On the other hand, the dark matter does not eject or captivate light and can only be perceived through its gravitational effects. It envelops the Universe for about 84 percent.

The scientists used the KMOS and SINFONI instruments at ESO's Very Large Telescope in Chile to gauge the rotation of six huge, star-forming galaxies in the distant Universe, at the height of the shaping of galaxy dated 10 billion years ago. They discovered that the outer areas of these distant galaxies were rotating more slowly than the areas near the center. This indicates that there is smaller dark matter present than previously thought, according to Phys.org.

Genzel said that there is an instability in the rotation velocities and these actually lessen further out in the galaxies. He also said that there are two probable causes for this case. He emphasized that most of the early huge galaxies were clearly governed by normal matter than the dark matter. Another cause is that these discs were much more unstable that the spiral galaxies.

The effects of these show that early galaxies were much more gas-rich and condense than the galaxies of today. These also indicate that 3 to 4 billion years after the Big Bang, the gas in galaxies reduced into flat and rotating discs. On the other hand, dark matter became much massive and scattered in the Universe, as it could be seen today.