I don't think our evidence for dark matter comes from interactions between galaxies but within a galaxy - the interaction of matter within the galaxy and the am

I don't think our evidence for dark matter comes from interactions between galaxies but within a galaxy - the interaction of matter within the galaxy and the amount of lensing observed because of the amount of observed matter in a galaxy - in other words I dont _think_ that this will do much to the dark matter calculations - but I am not certain and hope someone knowledgeable will come along and set us straight.