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

Abstract

We present a multi-wavelength study of the massive protocluster G286.21+0.17 (G286) using \emph{JWST} near-infrared 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 dense core G286c1. The H${}^{13}$CO${}^{+}$ emission confirms this HFS over [$-$19.2, $-$16.4]~km~s${}^{-1}$. The \emph{JWST} images further trace prominent photodissociation regions around the H\,{\sc ii}~region~A, powered by a B-type star. The radial distribution of ALMAGAL 1.38 mm core properties reveals steep power-law slopes toward the hub center. Within the inner hub (r < 8'', $\sim 0.1$~pc), the core number density follows $\ddot{I}[\mathrm{p}{\mathrm{c}}^{-2}]\propto {\mathrm{r}}^{-2.4\pm 0.5}$, the surface density scales as $\hat{I}\pounds [\mathrm{g}\mathrm{c}{\mathrm{m}}^{-2}]\propto {\mathrm{r}}^{-1.0\pm 0.2}$, and the enclosed core mass varies as $M_{\mathrm{core}}[M_{\odot }]\propto r^{-1.2\pm 0.2}$, while core diameters remain approximately constant ($D_{\mathrm{core}}[\mathrm{AU}]\propto {\mathrm{r}}^{-0.1\pm 0.1}$). These trends, along with filament mass accretion rates of $7\times 10^{-6}$--$1.8\times 10^{-4}$~$M_{\odot }$~yr${}^{-1}$, support a competitive accretion scenario in which gravitational focusing enhances core growth toward the hub center. Filament linewidths increase from tail/outer-region to head/hub-region, consistent with gravity-driven turbulence. However, the absence of a preferred alignment between velocity gradients and gravitational force directions may indicate a dynamically evolved system. The HFS likely formed through large-scale gas layer interactions and compression by the adjacent H\,{\sc ii} region. Overall, star formation in G286 appears regulated by filamentary accretion, competitive core growth in the hub, and stellar feedback.