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

TL;DR

This study uses 3-mm observations to analyze hierarchical fragmentation and gas dynamics in a massive star-forming region, revealing gravitationally bound cores, multiple outflows, and evidence of turbulence-driven fragmentation.

Contribution

It provides the first detailed picture of core structures and gas dynamics in IRDC G034.43+00.24, highlighting turbulence's role in hierarchical fragmentation and mass inflow processes.

Findings

Seven cores are gravitationally bound with virial parameter < 2.

At least four outflows with total mass ~45 M_sun and energy ~10^47 erg.

Evidence of turbulence-dominated hierarchical fragmentation at multiple scales.

Abstract

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+/H13CO+ 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 $\sim 45 M_\odot$, and a total energy of $\sim 1\times 10^{47}$ 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.