Characterizing Dust Extinction and Spatially Resolved Paschen-α Emission within 97 Galaxies at 1 < z < 1.6 with JWST NIRCam Slitless Spectroscopy
February 2026 • 2026ApJ...998..203L
Abstract • We present results on the Paschen-α (Paα) emitting galaxies observed as part of the JWST FRESCO survey in the GOODS-North and GOODS-South fields. Utilizing the JWST NIRCam wide field slitless spectroscopy (WFSS), we analyze emission line fluxes, star formation rates, and spatially resolved flux distributions of 97 Paα emitters at 1 < z < 1.6. To assess dust extinction within our sample, we combine Paα fluxes with archival Hα data taken with the Hubble Space Telescope WFC3 G141 grism. We employ 2D Paα and F444W mapping to trace the distributions of star formation and stellar mass, respectively. Our observations indicate that lower mass galaxies are almost dust free in Paα and exhibit smaller sizes both in star formation and underlying stellar continuum. In contrast, galaxies with stellar masses above 109.5M⊙ display diverse dust extinction and star formation patterns. This indicates that the structures and properties of massive galaxies evolve through different phases, which involve, e.g., star formation in massive clumps, compaction, and inside-out quenching. While average dust extinction rises with stellar mass, there is significant scatter among high-mass systems. This study demonstrates the capabilities of JWST WFSS in conducting systematic investigations of emission line galaxies and highlights the pivotal role of Paα in advancing our understanding of dust extinction and obscured star formation in the early Universe.
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