A Mid-infrared Spectroscopic Study of Young Stellar Objects in the SMC Region NGC 346: JWST Detects Dust, Accretion, Ices, and Outflows
December 2025 • 2025ApJ...995...22H
Abstract • We present mid-infrared spectroscopic observations of intermediate-to-high-mass young stellar objects (YSOs) in the low-metallicity star-forming region NGC 346 located within the Small Magellanic Cloud (SMC). We conduct these integral field unit observations with the Medium Resolution Spectroscopy mode of the Mid-Infrared Instrument on board JWST. The brightest and most active star-forming region in the SMC, NGC 346, has a metallicity of ∼1/5 Z⊙, analogous to the era when star formation in the early Universe (z ≃ 2) peaked. We discuss the emission and absorption features present in the spectral energy distributions (SEDs) of five YSOs with coverage from 4.9 to 27.9 μm and three other sources with partial spectral coverage. Via SED model fitting, we estimate their parameters, finding masses ranging from 2.9 to 18.0 M⊙. These targets show dusty silicates, polycyclic aromatic hydrocarbons, and ices of CO2, CO, H2O, and CH3OH in their protostellar envelopes. We measure emission from H2 and atomic fine-structure lines, suggesting the presence of protostellar jets and outflows. We detect H I lines, indicating ongoing accretion, and estimate accretion rates for each source that range from 2.50 × 10−6 to 2.23 × 10−4 M⊙ yr−1, based on the H I (7─6) line emission. We present evidence for a ∼30,000 au protostellar jet traced by fine-structure, H I, and H2 emission about YSO Y535—the first mid-infrared detection of a resolved protostellar outflow in the SMC and the most distant yet detected by JWST.
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