Filamentary accretion flows in high-mass star-forming clouds

Context: Filamentary accretion flows as gas-funneling mechanisms are a key aspect in high-mass star formation research. The kinematic properties along these structures are of particular interest.

Aims: This paper focuses on the question of whether gas is transported to dense clumps inside high-mass star-forming regions through filamentary structures, from scales of several parsecs down to the subparsec scale.

Methods: We quantified the gas flows from a scale of up to several parsecs down to the subparsec scale along filamentary structures. For this work the accretion flow mechanisms based on gas kinematic data in the three high-mass star-forming regions G75.78, IRAS21078+5211, and NGC7538 were studied with data obtained from the IRAM 30 m telescope. The analysis was carried out using the surface density derived from 1.2 mm continuum emission and velocity differences estimated from HCO + (1 − 0) and H 13 CO + (1 − 0) molecular line data.

Results: The mass flow behavior of the gas in the vicinity of high-mass star-forming clumps shows characteristic dynamical patterns, for example an increased mass flow rate toward the clumps. We assume that the velocity differences originate from filamentary-gas infall onto the high-mass star-forming clumps; however, the inclination of the filament structures along the line of sight is unknown. Nevertheless, using the velocity differences and mass surface densities, we can estimate the mean flow rates along the filamentary structures with respect to the line of sight and toward the clumps. We quantified the flow rates toward the clumps in a range from about 10 −3 M ⊙ yr −1 to 10 −5 M ⊙ yr −1 , inferred from clump-centered polar plots. Slight variations in the flow rates along the filamentary structures may be caused by overdensities and velocity gradients along the filaments.

Conclusions: While the initial studies presented here already reveal interesting results such as an increasing mass flow rate toward clumps, the properties of filamentary gas flows from large to small spatial scales, as well as potential variations over the evolutionary sequence, are subject to future studies.