ATOMS-QUARKS survey: Inflow and infall in massive Protocluster G318.049+00.086— evidence of competitive accretion

Abstract

We present a gas kinematic study of the massive protocluster G318.049+00.086. The protocluster is reported to contain 12 prestellar core candidates and four protostellar cores. Filamentary structures are identified using the 1.3 mm dust continuum map, with four of them converging into a dense central region, forming a hub-filament system. High velocity gradients (10─20 km s−1 pc−1) derived from position─velocity analysis of H13CO+ emission along three of those filaments are suggestive of mass inflow onto the central hub. A mass inflow rate higher than 103 M⊙ Myr−1 along the filaments indicates that the central hub is capable of forming massive star(s). Investigation of H13CO+ and CCH spectral profiles revealed the majority of the cores having the characteristic blue asymmetric line profiles, a typical signature of gravitational collapse. The remaining few cores showed red asymmetric profiles, indicative of gas expansion. Also, the derived mass infall rates for the protostellar cores in the hub region are significantly higher in comparison to those located along the filaments. The mass─radius relation of the cores revealed that the cores with red profiles reside in the massive star formation regime. However, the global velocity gradient along the filaments suggests that these particular cores are losing material to the hub. Our results support a competitive accretion scenario of massive star formation where gas is expected to be funnelled from less gravitationally dominant cores to the cores located at the gravitationally favorable position.