Molecular Clouds Surrounding Supernova Remnant G43.9+1.6: Associated and Nonassociated

Many supernova remnants (SNRs) are considered to evolve in molecular environments, but the associations between SNRs and molecular clouds (MCs) are often unclear. Being aware of such ambiguity, in our study, we report on the molecular environment toward SNR G43.9+1.6 through CO line observations. We investigated the correlations between the SNR and MCs at different velocities, and found two velocity components, i.e., similar to 5 km s(-1)and similar to 50 km s(-1), showing spatial correlations with the remnant. However, no kinematic evidence of a disturbance was found for the similar to 5 km s(-1)velocity component. Furthermore, at the distance of the similar to 5 km s(-1)velocity component, either near or far, the derived physical parameters are unreasonable. We conclude that the SNR is not associated with the similar to 5 km s(-1)velocity component, and their spatial correlation is just a chance correlation. For the similar to 50 km s(-1)velocity component, kinematic evidence of disturbances, as well as the spatial correlation, indicate that it is associated with the SNR. We found that all the CO spectra extracted from the molecular clumps distributed along the border of the remnant are with broadened components presented, which can be fitted by Gaussian functions. Through further analysis, we suggest that the SNR is at a near kinematic distance of about 3.1 kpc.