In 1933 (The year I was born incidentally) Zwicky calculated that the coma galaxy, in reality over 1000 galaxies clustered together in a sphere, was moving too fast to stay together.   This of course was based on the belief that gravity is an attraction of one mass for another. However an object such as the Coma or indeed any galaxy is not the same as the solar system.

Clearly if you take the idea that each particle in even a galaxy exerts the pull of gravity individually and has done so since it began its existence for possibly 13.7 Billion years.

Then since New Gravity is a pull on space, not on mass, it means that once clear of the limits of a galaxy it continues to infinity. So since space is pulled forever by each particle of a galaxy, the galaxy is pummelled from all directions by this ancient action of gravity forever. This if so magnifies the original effects of gravity and explains the Apparent mystery. The Milky Way is also shown to have a similar anomaly and this must apply to all galaxies. There is absolutely no need of Dark Matter the pull from even the outer edges will pull across all of  the galaxy and beyond the opposite outer edge thus reinforcing the power to keep the galaxy intact.