By the way, astronomical observations sets of interacting galaxies is just mark their position is anomalous in a single plane 4. Independence of the velocity of stellar systems, the distance from the center of the galaxy, similar to that mentioned above the behavior of pairs of objects (5), which may result from the actions of one and the same mechanism of interaction. If the analogy between the interaction of the above pairs and gravitational interactions of celestial bodies is legitimate, then independence of the speed of star systems on the distance from the galactic center, should be observed only for the galactic disk-shape. Introduction to the cosmological model of dark energy and dark matter gives explanation of the revealed facts, but at the same time concealing their essence, because no clear mechanism for the gravitational interaction. You can spend a lot of effort looking for what is not. May be appropriate to take another look at subject of research? In any case, an attempt to elucidate the mechanism of the gravitational interaction described in 5 shows the possibility of “do not multiply entities unnecessarily.” Sources: 1. Physics: Entsiklopediya. Ed..