The Dense Filamentary Giant Molecular Cloud G23.0-0.4: Birthplace of Ongoing Massive Star Formation

TL;DR

This study maps a massive, filamentary giant molecular cloud G23.0-0.4, revealing its structure, star formation activity, and potential relation to the Milky Way's spiral arms, highlighting turbulence-driven fragmentation.

Contribution

First detailed mapping of G23.0-0.4 revealing its filamentary structure, star formation sites, and connection to Galactic spiral density waves.

Findings

G23.0-0.4 is a large, dense, filamentary GMC with active star formation.

Star-forming clumps and masers are aligned along the filament, consistent with turbulence-driven fragmentation.

The GMC is likely located at the near side of the Scutum-Centaurus arm, related to spiral density waves.

Abstract

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 (~5E5Msun), large (~84x15 pc), and dense (~10E3 cm^-3) giant molecular cloud (GMC), G23.0-0.4 with VLSR~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 HII/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 0.18-0.26degree along the giant filament, which is consistent well with the theoretical predictions of 0.22degree. It indicates that the turbulence seems to dominate the fragmentation process of the dense gaseous filament on 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 has relation to the spiral density wave of the Milky Way.