Energy transfer from jets to surrounding matter to form lateral lobes in SS 433/W 50

Abstract We first investigate an approximate structure of the top region (TR) of a jet, sandwiched by a front shock from which the surrounding matter (SM) inflows and a rear shock from which the jet matter (JM) inflows. Since pressure in the TR is higher than that in the laterally outer space, both JM and SM flowing in the TR are pressed out from the side of the TR. Supposing a steady flow of SM and JM there, we construct a simplified two-dimensional model on a structure of the TR. With the help of the model, we next infer what happens when precessing jets go through the surroundings in the SS 433/W 50 system, presuming a supernova remnant (SNR) occupies W 50. If we assume reasonable density distributions of the SNR and the interstellar matter in a 10—100 pc distance range, the density of the surroundings is found to be much higher than that of the jet, such that the jet is largely braked in the TR and that the outflow rate of the energy from the side of the TR becomes almost identical to the intrinsic energy flow rate through the jet. The outflowing energy could spread to the ambient space in the form of a bow shock, but the situation of the shock propagation in the present case could be peculiar due to the presence of the precession. Particularly, all the mass and the energy outflowing from the inner side of the precession cone is considered to be concentrated around the axis of the precession cone. As the result, mass-compressed and energy-accumulated regions are expected to appear along the precession axis, which could be the origin of the lobes laterally extending from the main sphere of W 50 observed in radio and X-rays.