Kinematics of the western filament of W50

Abstract

ABSTRACT We study the kinematics of the western optical filament of the radio shell W50 with imaging Fabry–Perot spectroscopy using the [S ii] (λ6717 Å and λ6731 Å) line doublet. The high [S ii]/H α line ratio of this filament, as well as the complexity of the radial velocity profiles obtained in this work ensure that this filament and diffuse regions are the optical counterpart of W50 hosting the peculiar object SS 433. We derive a kinematical distance of 4.7 ± 0.5 kpc, validating a previously derived distance based on the assumption that H i or CO gas is associated with W50. Our distance estimate is in agreement with the distance to SS 433 derived from proper motions. Shock velocities of up to 120 km s−1 are estimated for the [S ii] emitting regions. We derive an age between 1.0 and 1.9 × 105 yr considering that W50 is a remnant of a supernova explosion or a bubble blown by the action of the jets of the central SS 433 source, respectively. Age values are compatible with the age of SS 433. We also estimate the energy deposited by the supernova in the interstellar medium and alternatively, the luminosity of a wind-blown bubble fed by the relativistic jets of SS 433, obtaining reasonable values. We examine the different scenarios for the formation of W50. We conclude that a supernova remnant scenario rejuvenated by the interaction of SS 433 jets, acting as a piston, evolving in a three-phase medium with photo-evaporation, describes better the different observations and theoretical models of this system.