A Systematic Study of Associations between Supernova Remnants and Molecular Clouds

We universally search for evidence of kinematic and spatial correlation of supernova remnant (SNR) and molecular cloud (MC) associations for nearly all SNRs in the coverage of the Milky Way Imaging Scroll Painting CO survey, i.e., 149 SNRs, 170 SNR candidates, and 18 pure pulsar wind nebulae in 1 degrees < l < 230 degrees and -5.degrees 5 < b < 5.degrees 5. Based on high-quality and unbiased (CO)-C-12/(CO)-C-13/(CO)-O-18 (J = 1-0) survey data, we apply automatic algorithms to identify broad lines and spatial correlations for molecular gas in each SNR region. The 91% of SNR-MC associations detected previously are identified in this paper by CO line emission. Overall, there could be as high as 80% of SNRs associated with MCs. The proportion of SNRs associated with MCs is high within the Galactic longitude less than similar to 50 degrees. Kinematic distances of all SNRs that are associated with MCs are estimated based on systemic velocities of associated MCs. The radii of SNRs associated with MCs follow a lognormal distribution, which peaks at similar to 8.1 pc. The progenitor initial mass of these SNRs follows a power-law distribution with an index of similar to-2.3 that is consistent with the Salpeter index of -2.35. We find that SNR-MC associations are mainly distributed in a thin disk along the Galactic plane, while a small number are distributed in a thick disk. With the height of these SNRs from the Galactic plane below similar to 45 pc, the distribution of the average radius relative to the height of them is roughly flat, and the average radius increases with the height when above similar to 45 pc.