An observation on shock waves in a dark matter medium

Using Newton s stellar balance equation in conjunction with the observed flat rotation velocities of satellite galaxies, we estimate the speed of sound in a dark matter medium. Our analysis reveals that the orbital velocities of these satellite galaxies significantly exceed the calculated sound speed. This disparity implies that the satellites traverse the dark matter medium at supersonic speeds, thereby giving rise to shock waves within it.Our observational study also supports this conclusion by examining nine spiral galaxies, where we consistently find that the inclination-corrected flat rotation velocities ( V flat ) surpass the dark matter sound speeds (cs). This disparity holds across a range of dark matter surface densities, demonstrating that supersonic motion and consequent shock wave generation are robust features in diverse galactic environments.