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Arxiv: When, Where, and How Star Formation Happens in a Galaxy Pair at Cosmic Noon Using CANUCS JWST/NIRISS Grism Spectroscopy Published: 6/21/2024 9:00:01 PM Updated: 6/21/2024 9:00:01 PM

Paper abstract: Spatially resolved studies are key to understanding when, where, and howstars form within galaxies. Using slitless grism spectra and broadband imagingfrom the CAnadian NIRISS Unbiased Cluster Survey (CANUCS) we study thespatially resolved properties of a strongly lensed (\mu = 5.4\pm1.8) z =0.8718 galaxy pair consisting of a blue face-on galaxy (10.2 \pm 0.2log(M/M_\odot)) with multiple star-forming clumps and a dusty red edge-ongalaxy (9.9 \pm 0.3 log(M/M_\odot)). We produce accurate H\alpha mapsfrom JWST/NIRISS grism data using a new methodology that accurately modelsspatially varying continuum and emission line strengths. With spatiallyresolved indicators, we probe star formation on timescales of ~ 10 Myr(NIRISS H\alpha emission line maps) and ~ 100 Myr (UV imaging andbroadband SED fits). Taking the ratio of the H\alpha to UV flux (\eta), wemeasure spatially resolved star formation burstiness. We find that in theface-on galaxy both H\alpha and broadband star formation rates (SFRs) drop atlarge galactocentric radii by a factor of ~ 4.7 and 3.8 respectively,while SFR over the last ~ 100 Myrs has increased by a factor of 1.6.Additionally, of the 20 clumps identified in the galaxy pair we find that 7 areexperiencing bursty star formation, while 10 clumps are quenching and 3 are inequilibrium (either being in a state of steady star formation or post-burst).Our analysis reveals that the blue face-on galaxy disk is predominantly in aquenching or equilibrium phase. However, the most intense quenching within thegalaxy is seen in the quenching clumps. This pilot study demonstrates whatJWST/NIRISS data can reveal about spatially varying star formation in galaxiesat Cosmic Noon.