Why do astronomers speak of Doppler equations and recession motion in connection to cosmic distance?
There is really no good reason other than vestigial –what once was a historical habit has become a quirk of specialized jargon. When astronomers use these Doppler equations or refer to recession velocities they are fully aware (at least the vast majority are) that it is the space expansion of intergalactic space that is causing the redshifting of light and not galactic Doppler motion through space.
