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

Abstract

We present new 3-mm continuum and molecular lines observations from the ATOMS\nsurvey towards the massive protostellar clump, MM1, located in the filamentary\ninfrared dark cloud (IRDC), G034.43+00.24 (G34). The lines observed are the\ntracers of either dense gas (e.g. HCO+/H13CO+ J = 1-0) or outflows (e.g. CS J =\n2-1). The most complete picture to date of seven cores in MM1 is revealed by\ndust continuum emission. These cores are found to be gravitationally bound,\nwith virial parameter, $\\alpha_{vir}<2$. At least four outflows are identified\nin MM1 with a total outflowing mass of $\\sim 45 M_\\odot$, and a total energy of\n$\\sim 1\\times 10^{47}$ erg, typical of outflows from a B0-type star. Evidence\nof hierarchical fragmentation, where turbulence dominates over thermal\npressure, is observed at both the cloud and the clump scales. This could be\nlinked to the scale-dependent, dynamical mass inflow/accretion on clump and\ncore scales. We therefore suggest that the G34 cloud could be undergoing a\ndynamical mass inflow/accretion process linked to the multiscale fragmentation,\nwhich leads to the sequential formation of fragments of the initial cloud,\nclumps, and ultimately dense cores, the sites of star formation.\n