The spread of velocities for the individual galaxies is about 800-1000 km/s.
The gravity of the dark matter is also thought to prevent individual galaxies from breaking to pieces.
Hot dark matter cannot explain how individual galaxies formed from the big bang.
The new Hubble observations continue the search for dark matter in individual galaxies.
Groups and clusters may contain ten to thousands of individual galaxies.
About 60 million years before the end, gravity would be too weak to hold the Milky Way and other individual galaxies together.
Although included in the double galaxies category, many of these objects are individual galaxies.
The telescope has also been used to measure the rotation of individual galaxies.
More advanced simulations are starting to include baryons and study the formation of individual galaxies.
The effect is too small to be measured for an individual galaxy.