The Large-scale Interstellar Medium of SS 433/W50 Revisited

With new high-resolution CO and H I data, we revisited the large-scale interstellar medium (ISM) environment toward the SS. 433/W50 system. We find that two interesting molecular cloud (MC) concentrations, G39.315 -1.155 and G40.331-4.302, are well aligned along the precession cone of SS 433 within a smaller opening angle of similar to +/- 7 degrees. The kinematic features of the two MCs at similar to 73-84 km s(-1), as well as those of the corresponding atomic-gas counterparts, are consistent with the kinematic characteristics of SS. 433. That is, the receding gas from SS. 433 jet is probably responsible for the redshifted feature of G39.315-1.155 near the Galactic plane, and the approaching one may power the blueshifted gas of G40.331-4.302 toward the observer. Moreover, the H I emission at V-LSR similar to 70-90 km s(-1) displays the morphological resemblance with the radio nebula W50. We suggest that the V-LSR = 77 +/- 5 km s(-1) gas is physically associated with SS. 433/W50, leading to a near kinematic distance of 4.9 +/- 0.4 kpc for the system. The observed gas features, which are located outside the current radio boundaries of W50, are probably the fossil record of jet-ISM interactions at similar to 10(5) years ago. The energetic jets of the unique microquasar have profound effects on its ISM environment, which may facilitate the formation of molecular gas on the timescale of less than or similar to 0.1 Myr for the ram pressure of similar to 2 x 10(6) K cm(-3).