Analytically derived colour-coded maps of several flow quantities, namely log pressure P in dyn cm^-2 (upper left panel), log density ρ in g cm^-3 (upper right panel), log temperature T in K (lower left panel), and the velocity ratio u/c_s ≃ M (lower right panel) for the SQ galaxy NGC 7318b at the time t = 130   Myr (j = 0, ). A perfect gas with γ = 5/3 and an upstream Mach number of M_∞ = 930 have been assumed.