Sokolov, V., Wang, K., Pineda, J. E., Caselli, P., Henshaw, J. D., Barnes, A. T., Tan, J. C., Fontani, F., Jiménez Serra, I. 2019. Multicomponent Kinematics in a Massive Filamentary Infrared Dark Cloud. Astrophysical Journal 872, 1, DOI: 10.3847/1538-4357/aafaff

To probe the initial conditions for high-mass star and cluster formation, we investigate the properties of dense filaments within the infrared dark cloud (IRDC) G035.39-00.33 (G035.39) in a combined Very Large Array and Green Bank Telescope mosaic tracing the NH3 (1, 1) and (2, 2) emission down to 0.08 pc scales. Using agglomerative hierarchical clustering on multiple line-of-sight velocity component fitting results, we identify seven extended velocity-coherent components in our data, likely representing spatially coherent physical structures, some exhibiting complex gas motions. The velocity gradient magnitude distribution peaks at its mode of 0.35 km s(-1) pc(-1) and has a long tail extending into higher values of 1.5-2 km s(-1) pc(-1), and it is generally consistent with those found toward the same cloud in other molecular tracers and with the values found toward nearby low-mass dense cloud cores at the same scales. Contrary to observational and theoretical expectations, we find the nonthermal ammonia line widths to be systematically narrower (by about 20%) than those of N2H+ (1-0) line transition observed with similar resolution. If the observed ordered velocity gradients represent the core envelope solid-body rotation, we estimate the specific angular momentum to be about 2. x. 10(21) cm(2) s(-1), similar to the low-mass star-forming cores. Together with the previous finding of subsonic motions in G035.39, our results demonstrate high levels of similarity between kinematics of a high-mass star-forming IRDC and the low-mass star formation regime.