Molecular clouds at the eastern edge of radio nebula W50

TL;DR

This study identifies new molecular clouds near the SS 433 jet at W50's eastern edge, suggesting possible interactions between the jet and surrounding interstellar medium, advancing understanding of jet-ISM dynamics.

Contribution

First detection of molecular clouds at the eastern edge of W50 near SS 433, indicating potential jet-ISM interaction effects.

Findings

Two molecular clouds identified with complex velocity structures.

One cloud shows a density gradient toward SS 433.

Possible jet-induced formation of molecular clouds.

Abstract

Microquasar SS 433 located at the geometric center of radio nebula W50 is a suitable source for investigating the physical process of how galactic jets affect the surrounding interstellar medium (ISM). Previous studies have searched for evidence of the interaction between the SS 433 jet and ISM, such as neutral hydrogen gas and molecular clouds; however, it is still unclear which ISM interacts with the jet. We looked for new molecular clouds that possibly interact at the terminal of the SS 433 eastern jet using the Nobeyama 45-m telescope and the Atacama Submillimeter Telescope Experiment (ASTE). We identified two molecular clouds, comprising many small clumps, in the velocity range of 30.1--36.5 km s$^{-1}$ for the first time. These clouds have complex velocity structures, and one of them has a density gradient toward SS 433. Although it is difficult to conclude the relation between the molecular clouds and the SS 433/W50 system, there is a possibility that the eastern structure of W50 constructed by the SS 433 jet swept up tiny molecular clumps drifting in the surroundings and formed the molecular clouds that we identified in this study.