Filamentary mass accretion towards the high-mass protobinary system G11.92-0.61 MM2

We present deep, sub-arcsecond (~2000 AU) resolution ALMA 0.82 mm observations of the former high-mass prestellar core candidate G11.92-0.61 MM2, recently shown to be an ~500 AU-separation protobinary. Our observations show that G11.92-0.61 MM2, located in the G11.92-0.61 protocluster, lies on a filamentary structure traced by 0.82 mm continuum and N₂H⁺(4-3) emission. The N₂H⁺(4-3) spectra are multi-peaked, indicative of multiple velocity components along the line of sight. To analyse the gas kinematics, we performed pixel-by-pixel Gaussian decomposition of the N₂H⁺ spectra using SCOUSEPY and hierarchical clustering of the extracted velocity components using ACORNS. Seventy velocity- and position-coherent clusters (called "trees") are identified in the N₂H⁺-emitting gas, with the 8 largest trees accounting for >60% of the fitted velocity components. The primary tree, with ~20% of the fitted velocity components, displays a roughly north-south velocity gradient along the filamentary structure traced by the 0.82 mm continuum. Analysing a ~0.17 pc-long substructure, we interpret its velocity gradient of ~10.5 km s⁻¹pc⁻¹ as tracing filamentary accretion towards MM2 and estimate a mass inflow rate of ~1.8×10⁻⁴ to 1.2×10⁻³ M_ yr⁻¹. Based on the recent detection of a bipolar molecular outflow associated with MM2, accretion onto the protobinary is ongoing, likely fed by the larger-scale filamentary accretion flows. If 50% of the filamentary inflow reaches the protostars, each member of the protobinary would attain a mass of 8 M_ within ~1.6×10⁵ yr, comparable to the combined timescale of the 70 μm- and MIR-weak phases derived for ATLASGAL-TOP100 massive clumps using chemical clocks.