Interaction between Supernova Remnant G22.7-0.2 and the Ambient Molecular Clouds

We have carried out ¹²CO (J = 1-0 and 2-1), ¹³CO (J = 1-0), and C¹⁸O (J = 1-0) observations in the direction of the supernova remnant (SNR) G22.7–0.2. A filamentary molecular gas structure, which is likely part of a larger molecular complex with V LSR ~ 75-79 km s^–1, is detected and is found to surround the southern boundary of the remnant. In particular, the high-velocity wing (77-110 km s^–1) in the ¹²CO (J = 1-0 and J = 2-1) emission shows convincing evidence of the interaction between SNR G22.7–0.2 and the 75-79 km s^–1 molecular clouds (MCs). Spectra with redshifted profiles, a signature of shocked molecular gas, are seen in the southeastern boundary of the remnant. The association between the remnant and the 77 km s^–1 MCs places the remnant at the near distance of 4.4 ± 0.4 kpc, which agrees with a location on the Scutum-Crux arm. We suggest that SNR G22.7–0.2, SNR W41, and H II region G022.760-0.485 are at the same distance and are associated with GMC G23.0–0.4.