Resolving dust and Lyman α emission in a lensed galaxy at the epoch of reionization with JWST/CANUCS

Lyman α (Lyα) emission is highly sensitive to dust and neutral hydrogen and is believed to be suppressed in dusty or hydrogen-rich galaxies -- especially during the epoch of reionization (EoR). Yet, moderately dusty Lyα emitters (LAEs) are observed at this epoch, suggesting that complex interstellar medium (ISM) geometries and feedback-driven outflows facilitate Lyα escape. We investigated the dust, gas, and stellar properties of the gravitationally lensed LAE HCM 6A at z = 6. 5676 to characterize its multiphase ISM structure and the physical conditions that regulate Lyα escape. We combined JWST/NIRISS slitless spectroscopy, HST+JWST/NIRCam imaging, and JWST/NIRSpec slit spectra from the CANUCS program. Using a customized spectral-energy-distribution-fitting framework with a flexible attenuation law, we derived spatially resolved stellar, nebular, and dust properties on integrated (approx1 kpc), slit-level (approx0. 1 kpc), and pixel-level (approx25 pc) measurements, thanks to strong lensing with a magnification of μ ≈ 8. 3-9. 1. A high-quality Lyα map from, a tool for extracting spatially resolved emission-line maps from slitless spectroscopy, traces the spatial distribution of Lyα emission. BAGPIPES SLEUTH We measure an unlensed stellar mass of łog M_* = 8. 3–8. 4 and an intrinsic UV magnitude of M_ ̊m UV = -19. 8 ± 0. 1. Slit-level measurements show that the oldest, most massive region (S1) is moderately dusty with consistent stellar (AV, β) and nebular (AV^̊m B, line-emission) indicators, implying a uniform ISM geometry, while the dust tracers of the youngest region (S3) are highly mismatched, revealing a complex, feedback-shaped multiphase ISM. Lyα emission arises primarily from S3. Pixel-level maps reveal a dust-cleared central clump (C3) where Lyα emerges, encircled by dustier outskirts, consistent with a very recent (łesssim 10 Myr) starburst that created Lyα escape channels. Next, slit-level maps show Calzetti-like attenuation curves with a UV bump that increases with stellar age and decreases with V-band attenuation (AV), with a tentative detection of a UV bump in S1 at ∼25% of the Milky Way amplitude. Pixel-level maps reveal that both the curve slope (S) and the UV bump (B) peak in the region between two clumps (C1 and C2), indicating dust-grain processing in a merger-driven starburst. Our observations provide a uniquely detailed, spatially resolved view of a moderately dusty LAE at the EoR, demonstrating how the interplay between multiphase ISM geometry and feedback governs Lyα escape. Constraining some key quantities requires fully resolved spectroscopy, which future JWST/NIRSpec integral field unit observations will provide.