Multiscale Mass-assembly Scenario in the High-mass Star-forming Filament IRAS 19368+2239 Observed as Part of the INFANT Survey

A multiscale dynamical mass-assembly scenario, where stars form through multiscale fragmentation and hierarchical gas infall from clouds to filaments, clumps, and cores, has been proposed for high-mass star formation, but the precise observational picture of gas dynamics across these scales remains limited. We investigate the hierarchical fragmentation and multiscale gas infall within the high-mass star-forming filament IRAS 19368+2239 (hereafter, I19368) using 1.3 mm continuum mosaic observations from the Atacama Large Millimeter/submillimeter Array INFANT survey at a spatial resolution of ∼2800 au, complemented by molecular line data (e.g., NH 3 , H 2CO ) tracing kinematics across different scales. The I19368 filament splits into two segments: a northern filament ( F N ) and a southern filament ( F S ). There are 15 dense cores along the filament, with 13 located in the denser F S . Most cores are gravitationally bound and have high mass surface densities (Σ ≳ 1 g cm −2 ), indicating their potential to form high-mass stars. The cloud exhibits hierarchical fragmentation; the filament fragments into clumps via a cylindrical mode, and the clumps subsequently fragment into cores via a spherical Jeans mode, with both processes likely driven by turbulence. We further find a cascade of mass infall rates, decreasing from ∼6.5 × 10 −4 M ⊙ yr −1 (cloud to filament) down to ∼(1−1.7) × 10 −5 M ⊙ yr −1 (core to protostar), which could be driven by hierarchical gravitational collapse. Together, these results reveal a concurrent process in I19368; gravity-driven, multiscale gas infall coexists with turbulence-driven, hierarchical fragmentation, leading to high-mass star formation, supporting the multiscale, dynamical mass-assembly scenario for high-mass star formation.