2019MNRAS.485.3334Z

We utilize multiple-waveband continuum and molecular-line data of CO isotopes to study the dynamical structure and physical properties of the IRDC G31.97+0.07. We derive the dust temperature and H₂ column density maps of the whole structure by spectral energy distribution fitting. The total mass is about 2.5×10⁵ M^_☉ for the whole filamentary structure and about 7.8×10⁴ M^_☉ for the infrared dark cloud (IRDC). Column density probability distribution functions (PDFs) produced from the column density map are generally in the power-law form, suggesting that this part is mainly gravity dominant. The flatter slope of the PDF of the IRDC implies that it might be compressed by an adjacent, larger H II region. There are 27 clumps identified from the 850 µm continuum located in this filamentary structure. Based on the average spacing of the fragments in the IRDC, we estimate the age of the IRDC. The age is about 6.4 Myr, assuming inclination angle i = 30°. For 18 clumps with relatively strong CO and ¹³CO (3-2) emission, we study their line profiles and stabilities. We find five clumps with blue profiles that indicate gas infall motion and two clumps with red profiles that indicate outflows or expansion. Only one clump has α_vir > 2, suggesting that most clumps are gravitationally bound and tend to collapse. In the mass-R_eq diagram, 23 of 27 clumps are above the threshold for high-mass star formation, suggesting that this region can be a good place for studying high-mass star forming.