Protoplanetary Disk Evolution in a Low-metallicity Environment: JWST's First Mid-infrared Census of Low-mass Stars

May 2026 • 2026ApJ..1002...73Y

Authors • Yasui, Chikako • Izumi, Natsuko • Saito, Masao • Lau, Ryan M. • Kobayashi, Naoto • Ressler, Michael E.

Abstract • This study presents the first high-resolution, high-sensitivity mid-infrared (MIR) investigation of protoplanetary disks in a low-metallicity environment, using JWST/NIRCam and MIRI observations of Digel Cloud 2, a star-forming region in the outer Galaxy (D ≃ 8 kpc, [M/H] ≃ ─0.7 dex). It hosts two very young (∼0.1 Myr) embedded clusters, Cloud 2-N and Cloud 2-S, offering a window into disk evolution under conditions analogous to the early Universe, where low metallicity implies reduced dust content. Imaging across 1─20 μm, including F770W and complementary bands (F356W, F444W, F405N), enables probing disk properties with unprecedented spatial resolution and stellar mass sensitivity down to ∼0.1 M_⊙. Among 89 and 95 sources detected in F770W in Cloud 2-N and 2-S, respectively, we identify candidate stellar-mass cluster members using infrared photometry, from which stellar mass and extinction are estimated. Among these, ≃75% retain optically thick disks in both clusters based on MIR spectral energy distribution slopes, consistent with similarly aged solar-metallicity regions. In contrast, a lack of 2 μm excess suggests diminished inner disk emission, possibly due to enhanced silicate grains with low sublimation temperatures. Using the F405N narrowband filter covering Brα, we detect accretion signatures in ≃35% of sources selected by extinction criteria, with rates ≳10⁻⁶ M_⊙ yr⁻¹, comparable to or exceeding those in nearby low-mass stars. Brown dwarf candidates, identified across multiple bands including F770W and shorter wavelengths, exhibit a high disk fraction of ∼75%, indicating robust disk retention across mass ranges even under low-metallicity conditions.

Links

• SIMBAD https://simbad.u-strasbg.fr/simbad/sim-ref?querymethod=bib&simbo=on&submit=submit+bibcode&bibcode=2026ApJ..1002...73Y
• PDF https://iopscience.iop.org/article/10.3847/1538-4357/ae56fe/pdf
• PREPRINT http://arxiv.org/abs/2603.29007
• DATA https://archive.stsci.edu/mastbibref.php?bibcode=2026ApJ..1002...73Y
• DATA https://doi.org/10.17909/a2k0-tf62
• ELECTR https://doi.org/10.3847/1538-4357/ae56fe