Constraints on the angle θ between the jet and the line of sight and the jet velocity β in units of the speed of light. Blue and black curves correspond to J = 100 and β_a = 1.2, respectively. The red curve is from the P_c versus P_tot relation. The dot-dashed red lines are obtained allowing the core density to vary by a factor two. The gray area corresponds to the permitted values of β and θ.