2015ApJ...811..134S

We present observations of 1.5 square degree maps of the ¹²CO, ¹³CO, and C¹⁸O (J = 1 - 0) emission toward the complex region of the supernova remnant (SNR) W41 and SNR G22.7-0.2. A massive (), large (∼84x15 pc), and dense (∼10³/cm3) giant molecular cloud (GMC), G23.0-0.4 with 77 km/s, is found to be adjacent to the two SNRs. The GMC displays a filamentary structure approximately along the Galactic plane. The filamentary structure of the dense molecular gas, traced by C¹⁸O (J = 1 - 0) emission, is also coincident well with the distribution of the dust-continuum emission in the direction. Two dense massive MC clumps, two 6.7 GHz methanol masers, and one H ii/SNR complex, associated with the 77 km/s GMC G23.0-0.4, are aligned along the filamentary structure, indicating the star-forming activity within the GMC. These sources have periodic projected spacing of 0.°18-0.°26 along the giant filament, which is consistent with the theoretical predictions of 0.°22. This indicates that the turbulence seems to dominate the fragmentation process of the dense gaseous filament on a large scale. The established 4.4 kpc distance of the GMC and the long dense filament traced by C¹⁸O emission, together with the rich massive star-formation groups in the nearby region, suggest that G23.0-0.4 is probably located at the near side of the Scutum-Centaurus arm in the first quadrant. Considering the large scale and the elongation structure along the Galactic plane, we speculate that the dense filamentary GMC is related to the spiral density wave of the Milky Way.