We present investigations of the interaction between the relativistic, precessing jets of the microquasar SS 433 and the surrounding, expanding supernova remnant (SNR) shell, W 50, and the consequent evolution in the inhomogeneous interstellar medium (ISM). We model their evolution using the hydrodynamic FLASH code, which uses adaptive mesh refinement. We show that the peculiar morphology of the entire nebula can be reproduced to a good approximation, due to the combined effects of (i) the evolution of the SNR shell from the free-expansion phase through the Sedov blast wave in an exponential density profile from the Milky Way disc, and (ii) the subsequent interaction of the relativistic, precessing jets of SS 433. Our simulations reveal: (1) Independent measurement of the Galaxy scaleheight and density local to SS 433 (as n 0 = 0.2 cm −3 , Z d = 40 pc), with this scaleheight being in excellent agreement with the work of Dehnen & Binney.(2) A new mechanism for hydrodynamic refocusing of conical jets.(3) The current jet precession characteristics do not simply extrapolate back to produce the lobes of W 50, but a history of episodic jet activity having at least three different outbursts with different precession characteristics would be sufficient to produce the W 50 nebula. A history of intermittent episodes of jet activity from SS 433 is also suggested in a kinematic study of W 50 detailed in a companion paper. (4) An estimate of the age of W 50, and equivalently the age of SS 433's black hole created during the supernova explosion, in the range of 17 000-21 000 yr.

The compelling evidence for a connection between SS 433 and W50 has provoked much imagination for decades. There are still many unanswered questions: What was the nature of the progenitor of the compact object in SS 433? What causes the evident re-collimation in SS 433's jets? How recent is SS 433's current precession state? What mass and energy contributions from a possible supernova explosion are required to produce W50? Here we comment on two of our 53 models: (i) featuring the SNR evolution alone, and (ii) the SNR combined with a simple jet model.

We present the results of a kinematical study of the W 50 nebula using high-resolution radio observations from the Very Large Array spanning a 12-yr period, sampled in 1984, 1993 and 1996. We conduct a careful analysis of the proper motions of the radio filaments across the W 50 nebula at each epoch and detect no significant motion for them during this period. The apparent lack of movement in the radio filaments mandates either (i) a high degree of deceleration of SS 433's jet ejecta in the W 50 nebula; or (ii) that the lobes of W 50 formed a long time ago in SS 433's history, during a jet outburst with appreciably different characteristics from the well-known precessing jet state observed in SS 433 at the present day. We discuss the possible scenarios which could explain this result, with relevance to the nature of SS 433's current jet activity.

We present new Giant Metre‐wave Radio Telescope (GMRT) observations of Hubble Deep Field (HDF) 130, an inverse‐Compton (IC) ghost of a giant radio source that is no longer being powered by jets. We compare the properties of HDF 130 with the new and important constraint of the upper limit of the radio flux density at 240 MHz to an analytic model. We learn what values of physical parameters in the model for the dynamics and evolution of the radio luminosity and X‐ray luminosity [due to IC scattering of the cosmic microwave background (CMB)] of a Fanaroff–Riley type II (FR II) source are able to describe a source with features (lobe length, axial ratio, X‐ray luminosity, photon index and upper limit of radio luminosity) similar to those of the observations. HDF 130 is found to agree with the interpretation that it is an IC ghost of a powerful double‐lobed radio source, and we are observing it at least a few Myr after jet activity (which lasted 5–100 Myr) has ceased. The minimum Lorentz factor of injected particles into the lobes from the hotspot is preferred to be γ∼ 103 for the model to describe the observed quantities well, assuming that the magnetic energy density, electron energy density and lobe pressure at time of injection into the lobe are linked by constant factors according to a minimum energy argument, so that the minimum Lorentz factor is constrained by the lobe pressure. We also apply the model to match the features of 6C 0905+3955, a classical double FR II galaxy thought to have a low‐energy cut‐off of γ∼ 104 in the hotspot due to a lack of hotspot IC X‐ray emission. The models suggest that the low‐energy cut‐off in the hotspots of 6C 0905+3955 is γ≳ 103, just slightly above the particles required for X‐ray emission.

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