The ubiquitous presence of dark matter in the universe is today a central tenet in modern cosmology and astrophysics. (sciencedaily.com)
In a paper to appear in Publications of the Astronomical Society of Australia, Forbes and Kroupa have offered five possible criteria for determining whether an object is a galaxy: the presence of dark matter, multiple generations of stars, satellite star clusters, a minimum size, and the time it takes for gravitational interactions between stars to slow them all down to roughly the same speed. (newscientist.com)
For example, the presence of dark matter helps explain why our galaxy is stable. (discovermagazine.com)