We investigate the properties of spiral shocks in a steady, adiabatic, non-axisymmetric, self-gravitating, mass-outflowing accretion disk around a compact object. We obtained the accretion-ejection solutions in a galactic disk and applied them to spiral galaxies in order to investigate the possible physical connections between some observational quantities of galaxies. We considered the self-gravitating disk potential to examine the properties of the galactic gaseous disk. We obtained spiral shock-induced accretion-ejection solutions following the point-wise self-similar approach. We observed that the self-gravitating disk profoundly affects the dynamics of the spiral structure of the disk and the properties of the spiral shocks. We find that the observational dispersion between the pitch angle and shear rate and between the pitch angle and star formation rate in spiral galaxies contains some important physical information. There are large differences among the star formation rates of galaxies with similar pitch angles. These differences may be explained by the different star formation efficiencies caused by distinct galactic ambient conditions.