ATOMS: ALMA Three-millimeter Observations of Massive Star-forming regions - V. Hierarchical fragmentation and gas dynamics in IRDC G034.43+00.24

We present new 3-mm continuum and molecular lines observations from the ATOMS survey towards the massive protostellar clump, MM1, located in the filamentary infrared dark cloud (IRDC), G034.43+00.24 (G34). The lines observed are the tracers of either dense gas (e.g. HCO+/(HCO+)-C-13 J= 1-0) or outflows (e.g. CS J = 2-1). The most complete picture to date of seven cores in MM1 is revealed by dust continuum emission. These cores are found to be gravitationally bound, with virial parameter, alpha(vir) < 2. At least four outflows are identified in MM1 with a total outflowing mass of similar to 45 M-circle dot, and a total energy of 1 x 10(47) erg, typical of outflows from a B0-type star. Evidence of hierarchical fragmentation, where turbulence dominates over thermal pressure, is observed at both the cloud and the clump scales. This could be linked to the scale-dependent, dynamical mass inflow/accretion on clump and core scales. We therefore suggest that the G34 cloud could be undergoing a dynamical mass inflow/accretion process linked to the multiscale fragmentation, which leads to the sequential formation of fragments of the initial cloud, clumps, and ultimately dense cores, the sites of star formation.

Automated summary

New observations of the massive protostellar clump MM1 in the infrared dark cloud G34 reveal a detailed picture of its seven cores. These cores are found to be gravitationally bound and show evidence of outflows, indicating a dynamic mass inflow/accretion process leading to star formation.