Dust-embedded Star Formation: Bridging Magellanic Cloud Studies of Massive Young Stellar Objects to Nearby Spiral Galaxies
August 2026 • 2026ApJ..1006..144R
Abstract • We use JWST NIRCam and MIRI imaging at 2, 4, 10, and 21 μm to study young, dusty compact sources in four nearby galaxies at distances of ∼1─5 Mpc (M33, NGC 300, NGC 7793, and NGC 5068). This work bridges well-characterized massive young stellar objects (MYSOs) in the Magellanic Clouds from the Spitzer Space Telescope SAGE survey to new studies of embedded clusters in more distant galaxies with JWST. Guided by the SAGE-LMC catalog, we define JWST color─magnitude selection criteria (F1000W versus F1000W − F2100W) and test them using resolution-degradation experiments. We identify 216, 32, 80, and 139 dusty young objects in the four galaxies, respectively. The selected population spans sources from systems dominated by a single MYSO to compact marginally resolved sources hosting multiple MYSOs. The color selection remains stable across 1─5 Mpc, and the 10 μm luminosity function retains a slope of α ∼ −2. However, blending and surface-brightness dilution remove fainter sources, leading to incompleteness of up to ∼50% at 5.2 Mpc and biasing the sample toward brighter objects (F1000W < 19 mag). The sample spans approximate stellar masses of ∼10─2 × 105 M⊙. Spatial resolution affects the interpretation of mid-IR emission: clustering increases the fraction of emission attributed to compact sources in active regions, while blending into diffuse emission dominates in quiescent environments. Comparisons with polycyclic aromatic hydrocarbon (PAH)-selected young clusters in the PHANGS galaxy NGC 5068 show that our selection recovers ∼80% of the PAH-selected sources. We show that the practical limit for studying individual MYSOs with JWST is ∼3 Mpc. The resulting catalog provides a foundation for future resolved studies of star formation rates and early cluster evolution.
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