Continuous Jets and Backflow Models for the Formation of W50/SS433 in Magnetohydrodynamics Simulations

TL;DR

This study uses magnetohydrodynamics simulations to explore how light jets and backflow dynamics can explain the formation and morphology of the W50/SS433 system, linking jet interactions to observed hotspots.

Contribution

It introduces a new jet-based formation scenario for W50/SS433, emphasizing the role of backflow and shock interactions in shaping the nebula.

Findings

Light jets develop spheroidal shapes early on.

Shell and wings form from broadening spherical cocoon.

Oblique shocks dissipate most jet kinetic energy, aligning with observed hotspots.

Abstract

The formation mechanism of the W50/SS433 complex has long been a mystery. We propose a new scenario in which the SS433 jets themselves form the W50/SS433 system. We carry out magnetohydrodynamics simulations of two-side jet propagation using the public code CANS+. As found in previous jet studies, when the propagating jet is lighter than the surrounding medium, the shocked plasma flows back from the jet tip to the core. We find that the morphology of light jets is spheroidal at early times, and afterward, the shell and wings are developed by the broadening spherical cocoon. The morphology strongly depends on the density ratio of the injected jet to the surrounding medium. Meanwhile, the ratio of the lengths of the two-side jets depends only on the density profile of the surrounding medium. We also find that most of the jet kinetic energy is dissipated at the oblique shock formed by the interaction between the backflow and beam flow, rather than at the jet terminal shock. The position of the oblique shock is spatially consistent with the X-ray and TeV gamma-ray hotspots of W50.