Dana Makarova | Searcharxiv

arXiv2026

Discovery of a Compact Hub-Filament System in G286.21+0.17 with JWST and ALMA: Insights into Protocluster Formation and Competitive Accretion

We present a multi-wavelength study of the massive protocluster G286.21+0.17 (G286) using \emph{JWST} near-infrared (NIR) imaging and ALMA H$^{13}$CO$^{+}$(1--0) observations. The \emph{JWST} images uncover a compact ($\sim$0.5 pc) hub-filament system (HFS), comprising a dense central hub connected by at least four converging filaments seen in absorption, along with multiple H$_2$ protostellar jets/outflows. The hub hosts the dense core G286c1. H$^{13}$CO$^{+}$ emission confirms this HFS over [$-$19.2, $-$16.4]~km~s$^{-1}$, while the \emph{JWST} images also trace prominent photodissociation regions surrounding H\,{\sc ii}~region~A, powered by a B-type star. The identified H$^{13}$CO$^{+}$ skeletons closely trace the major \emph{JWST} absorption structures and show steep velocity gradients indicative of inflow. The radial distribution of ALMA 1.3 mm continuum cores (ALMAGAL and Cheng et al. 2020) exhibits power-law trends toward the hub center. The core number density, surface density, and core mass follow $Y \propto r^α$ with $α_ρ$ $\sim$$-$2.8 to $-$1.1, $α_Σ$ $\sim$$-$0.4 to $-$0.6, and $α_M$ $\sim$$-$0.7, whereas the core diameter remains nearly constant. Together with filament mass accretion rates of 7.6--11$\times10^{-5}$ M$_\odot$ yr$^{-1}$, these results are consistent with competitive accretion, highlighting preferential core growth toward the hub. Increasing filament linewidths toward the hub imply gravity-driven inflow, but misaligned local velocity gradient and gravitational force directions along filaments point to a dynamically evolved system. The HFS likely formed through large-scale gas-layer interactions aided by compression from the adjacent H\,{\sc ii} region. Overall, star formation in G286 appears to be regulated by filamentary accretion, competitive core growth in the hub, and stellar feedback.

astro-ph.GA↗

arXiv2026

Hub-filament systems and the growth of massive stars: episodic accretion, clustered environments, and projection effects

The processes controlling the early mass growth of future massive stars remain poorly understood, particularly the connection of this growth to star clustering and hub-filament systems (HFSs). This connection is difficult to establish observationally, because projection effects and line-of-sight confusion in position-position-velocity (PPV) data can distort the information about the intrinsic filamentary structure. To investigate this connection, we used a three-dimensional magnetohydrodynamic (MHD) simulation of star formation, where stars are represented by accreting sink particles. We identify clustered stellar environments, reconstruct time-dependent accretion histories, and investigate the relation between enhanced-accretion episodes and the locations of HFSs. We also use line radiative transfer modeling to produce synthetic molecular-line observations and examine how the same structures appear in projected PPV data. In our simulation, we find that 80% of future massive stars are associated with clustered environments. Their growth is also highly episodic: typically, about 40% of the accreted mass is gained during periods of enhanced accretion that occupy only about 10% of the total growth time. Periods of enhanced accretion occur slightly closer to three-dimensional HFS proxies, suggesting a possible link between HFS morphology and episodic accretion in future massive stars. Overall, our results suggest that the early growth of future massive stars is connected to both their clustered environment and the HFS structure of the surrounding gas, and projection effects must be considered when interpreting HFS in PPV data.

astro-ph.GA↗