Energy transfer from jets to surrounding matter to form lateral lobes in SS433/W50

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 help of the model, we next infer what happens when precessing jets go through the surroundings in the SS433-W50 system presuming a supernova remnant (SNR) occupies W50. If we assume reasonable density distributions of the SNR and the interstellar matter in a 10 $\sim$ 100 pc distance range, the density of the surroundings is found to be much higher than that of the jet so that the jet is largely braked in the TR and that outflowing 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 a 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 W50 observed in radio and X-rays.

Figures (4)

• Figure 1: Schematic cross section of a top region (TR) of a jet in the observational frame (a) and in the TR rest frame (b). Alt text: two pictures show the basic configuration of the model.
• Figure 2: Assumed density distributions of the SNR, the ISM and the jet (top), calculated velocity of the TR relative to the intrinsic jet velocity (middle) and calculated energy outflow rate from the TR relative to the intrinsic energy flow rate through the jet (bottom). Alt text: Two line graphs. x axis shows distance of a jet element from 10 pc to 100 pc commonly to the three panels. y axis shows densities of the jet and surrounding matters from 10$^{-32}$ to 10$^{-24}$ g/cc in the top panel, the relative velocity from 10$^{-3}$ to 1 in the middle panel and the relative energy loss rate from 0.9 to 1 in the bottom panel,
• Figure 3: Schematic pictures showing outflow-directions from the TR of the precessing jet for a time-interval over one precession-period. Cross sections along (left) and perpendicular to (right) the precessing axis are presented. Alt text: Pictures show the peculiar situation of the energy flows.
• Figure 4: Schematic diagram of stream lines of SM across a bow shock formed by interaction of the SM and a precessing jet on a meridian plane around the precession axis in the bow-shock rest frame. Short-dashed lines, A to B and A to C indicate the bow shock. Long-dashed lines, A' - F, and A' - D - E express the contact discontinuity between the swept up SM regions and the ejected JM regions. The SM flowing into on the inner side of the precession cone is considered to form an oblique bounce shock (dashed line between B and D) around the precession axis and eventually accumulate in the compressed region on the down-stream side of the bounce shock. Alt text: Picture shows a process to form the compressed region.