Characterizing Dust Extinction and Spatially Resolved Paschen- α Emission within 97 Galaxies at 1 < z < 1.6 with JWST NIRCam Slitless Spectroscopy

Abstract We present results on the Paschen- α (Pa α ) 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 Pa α emitters at 1 < z < 1.6. To assess dust extinction within our sample, we combine Pa α fluxes with archival H α data taken with the Hubble Space Telescope WFC3 G141 grism. We employ 2D Pa α 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 Pa α and exhibit smaller sizes both in star formation and underlying stellar continuum. In contrast, galaxies with stellar masses above 10 9.5 M ⊙ 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 Pa α in advancing our understanding of dust extinction and obscured star formation in the early Universe.