High-resolution radio observations of W50, the remnant associated with SS 433

Abstract

The NRAO VLA has been used to observe the radio source W50 with 30 arcsec and 1 arcmin resolutions at 20 cm. It is found that the overall structure of W50 is well delineated by filamentary structure. W50 possesses a nearly circular shell reminiscent of an evolved supernova remnant such as CTB1 and the Cygnus Loop. The most unusual features of W50 are the edge-brightened radio ears which extend beyond the shell. These ears appear morphologically distinct from the shell and have minimum energy pressures three times greater than are present in the shell. Thus, while no direct connection is observed between SS433 and the ears, it is suggested that the ears are the result of the interaction of the ram pressure of the collimated jets of SS433 with a supernova remnant shell. At 30 arcsec resolution the western ear of W50 is depolarized, suggesting that W50 and S74 are at a common distance of about 3 kpc.