Abstract

We present ALMA Band-3/7 observations towards "the Heart' of a massive hub-filament system (HFS) SDC335, to investigate its fragmentation and accretion. At a resolution of similar to 0.03 pc, 3 mm continuum emission resolves two massive dense cores MM1 and MM2, with 383((+234)(-120)) M-? (10-24 % mass of "the Heart') and 74((+47)(-24))M-?, respectively. With a resolution down to 0.01 pc, 0.87 mm continuum emission shows MM1 further fragments into six condensations and multi-transition lines of H2CS provide temperature estimation. The relation between separation and mass of condensations at a scale of 0.01 pc favors turbulent Jeans fragmentation where the turbulence seems to be scale-free rather than scale-dependent. We use the (HCO+)-C-13 J = 1 - 0 emission line to resolve the complex gas motion inside "the Heart' in position-position-velocity space. We identify four major gas streams connected to large-scale filaments, inheriting the anti-clockwise spiral pattern. Along these streams, gas feeds the central massive core MM1. Assuming an inclination angle of 45(+/- 15)degrees and a (HCO+)-C-13 abundance of 5(+/- 3) x 10(-11), the total mass infall rate is estimated to be 2.40(+/- 0.78) x 10(-3) M-? yr(-1), numerically consistent with the accretion rates derived from the clump-scale spherical infall model and the core-scale outflows. The consistency suggests a continuous, near steady-state, and efficient accretion from global collapse, therefore ensuring core feeding. Our comprehensive study of SDC335 showcases the detailed gas kinematics in a prototypical massive infalling clump, and calls for further systematic and statistical studies in a large sample.