Answer:
The red shift "proves" that the galaxies are attracted by a central force and are in Continuity Condition. The larger the red shift, the larger the central attraction.
The red shift is the cosine of the angle between the velocity and the radius cos(VR). The cosine is max when the the angle is zero or the velocity is parallel to the central radius. The cosine is zero when the angle is 90 degrees or the velocity is perpendicular to the radius with no central attraction.