The Amount of Dark Matter in Spiral Galaxies

The maximum' disk hypothesis of galactic disks imbedded in dark matter halos is examined. First, decompositions of the rotation curves of NGC 2613, 3198, 6503, and 7184 are analyzed. For these galaxies the radial velocity dispersions of the stars have been measured. If the parameters of the decompositions are chosen according to the maximum’ disk hypothesis, the Toomre Q stability parameter is sytematically less than one, which is a strong argument against the maximum' disk hypothesis. Next, density wave theory arguments are used to describe the morphology of the spiral arms of NGC 3223, 157, and 7083. It is shown that the maximum’ disk hypothesis is not consistent with the observed morphologies of the galaxies.