Molecular clouds at the eastern edge of radio nebula W50

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.