Density map of the two vortex families in a shadowing depiction that brings out the small scale structures. Top: incompressible vortex with an amplitude 90% larger than the background density; some weak spiral waves are excited by the vortex. Bottom: compressible vortex with an amplitude about 60% larger than the background value; two spiral waves are excited, with a density perturbation nearly equal to half the amplitude of the vortex.