A Mid-Infrared Spectroscopic Study of Young Stellar Objects in the SMC Region NGC 346: JWST Detects Dust, Accretion, Ices and Outflows

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 Mid-Infrared Instrument / Medium Resolution Spectroscopy 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 - 27.9 µm and three other sources with partial spectral coverage. Via SED model-fitting, we estimate their parameters, finding masses ranging from 2.9-18.0 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 which range from 2.50×10−6 -2.23×10−4 M⊙ yr−1 based on H I (7-6) line emission. We present evidence for a ∼ 30,000AU protostellar jet traced by fine-structure, H I and H2 emission about the YSO Y535, the first detection of a resolved protostellar outflow in the SMC, and the most distant yet detected.