Uncovering the hidden physical structures and protostellar activities in the Low-Metallicity S284-RE region: results from ALMA and JWST

Abstract

We present an observational study of the S284-RE region, a low-metallicity area associated with the extended S284 HII region. A thermally supercritical filament (mass $\sim$2402 $M_{\odot}$, length $\sim$8.5 pc) is investigated using the Herschel column density map. The Spitzer ratio 4.5 $\mu$m/3.6 $\mu$m map traces the H$_{2}$ outflows in this filament, where previously reported young stellar objects (YSOs) are spatially distributed. Analysis of the YSO distribution has revealed three active star-forming clusters (YCl1, YCl2, YCl3) within the filament. YCl3 seems to be the most evolved, YCl2 the youngest, while YCl1 displays signs of non-thermal fragmentation. The JWST (F470N+F444W)/F356W ratio map reveals at least seven bipolar H$_{2}$ outflows, with four (olc1--olc4) in YCl1 and three (ol1--ol3) in YCl2. The driving sources of these outflows are identified based on outflow geometry, ALMA continuum peaks, and YSO positions. Two ALMA continuum sources, #2 and #3, from the $M$-$R_{\rm eff}$ plot are recognized as potential massive star formation candidates. The ALMA continuum source #2 hosts at least three outflow-driving sources, whereas the ALMA continuum source #3 contains two. The bipolar outflow olc1, driven by an embedded object within the continuum source #2, is likely a massive protostar, as indicated by Br-$\alpha$ and PAH emissions depicted in the JWST (F405N+F444W)/F356W ratio map. The presence of H$_{2}$ knots in the outflows olc1 and ol1 suggests episodic accretion. Overall, the study investigates a massive protostar candidate, driving the $\sim$2.7 pc H$_{2}$ outflow olc1 and undergoing episodic accretion.