Jets of SS 433 on scales of dozens of parsecs

Abstract

The radio nebula W50 harbours the relativistic binary system SS433, which is a source of the powerful wind and jets. The origin of W50 is wrapped in the interplay of the wind, supernova remnant and jets. The evolution of the jets on the scales of the nebula is a Rosetta stone for its origin. To disentangle the roles of these components, we study physical conditions of the jets propagation inside W50, and determine deceleration of the jets. The morphology and parameters of the interior of W50 are analyzed using the available observations of the eastern X-ray lobe, which traces the jet. In order to estimate deceleration of this jet, we devised a simplistic model of the viscous interaction, via turbulence, of a jet with the ambient medium, which would fit mass entrainment from the ambient medium into the jets of the radio galaxy 3C31, the well studied case of continuously decelerating jets. X-ray observations suggest that the eastern jet persists through W50 as hollow one, and is recollimated to the opening $\sim 30^\circ$. From the thermal emission of the eastern X-ray lobe, we determine a pressure of $P \sim 3\cdot 10^{-11}$ erg/cm$^3$ inside W50. In the frame of a theory of the dynamics of radiative supernova remnants and stellar wind bubbles, this pressure in combination with other known parameters restricts W50's origin to a supernova happened $\sim 100\,000$ yr ago. Also, this pressure in our entrainment model gives a deceleration of the jet by $\sim 60\%$ in the bounds of W50's spherical component, of radius $\sim 40$ pc. In this case, the age of the jet should be $\ll 27\,000$ yr so as to satisfy the sphericity of W50. The entrainment model comes to the viscous stress in a jet of a form $\sigma = \alpha P$, where the viscosity parameter $\alpha$ is predefined by the model.