The discussion centers on the paper by F. I. Cooperstock and S. Tieu, which proposes that galaxy rotation can be explained through a model of stationary axially symmetric pressure-free fluids in general relativity, eliminating the need for dark matter. The authors demonstrate that the rotation curves of the Milky Way, NGC 3031, NGC 3198, and NGC 7331 align with mass density distributions of visible matter in flattened disks. They establish a luminous mass density threshold of 10^{-21.75} kg.m-3, challenging conventional dark matter theories.
PREREQUISITESAstronomers, astrophysicists, cosmologists, and students interested in alternative theories of galaxy dynamics and the role of dark matter in the universe.
Authors: F. I. Cooperstock, S. Tieu
A galaxy is modeled as a stationary axially symmetric pressure-free fluid in general relativity. For the weak gravitational fields under consideration, the field equations and the equations of motion ultimately lead to one linear and one nonlinear equation relating the angular velocity to the fluid density. It is shown that the rotation curves for the Milky Way, NGC 3031, NGC 3198 and NGC 7331 are consistent with the mass density distributions of the visible matter concentrated in flattened disks. Thus the need for a massive halo of exotic dark matter is removed. For these galaxies we determine the mass density for the luminous threshold as 10^{-21.75} kg.m$^{-3}.