Galactic Wakes

The hypersonic flow of intergalactic gas past a spherical galaxy is discussed. Isentropic motion near the downstream symmetry axis is described by a similarity solution to the fluid-dynamical equations. The upstream flow is represented by orbit theory and matched to the fluid flow across a conical shock. The downstream flow exhibits high density and low temperature near the axis. These results are used to estimate the X-radiation from galactic wakes.