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Arxiv: JWST PRIMER: A lack of outshining in four normal z =4-6 galaxies from the ALMA-CRISTAL Survey Published: 9/17/2024 11:00:05 AM Updated: 9/17/2024 11:00:05 AM

Paper abstract: We present a spatially resolved analysis of four star-forming galaxies at z= 4.44-5.64 using data from the JWST PRIMER and ALMA-CRISTAL surveys to probethe stellar and inter-stellar medium properties on the sub-kpc scale. In the1-5\,\mu{\rm m} JWST NIRCam imaging we find that the galaxies are composed ofmultiple clumps (between 2 and ~ 8) separated by ~eq 5\,{\rm kpc},with comparable morphologies and sizes in the rest-frame UV and optical. UsingBAGPIPES to perform pixel-by-pixel SED fitting to the JWST data we show thatthe SFR (~eq 25\,{\rm M}_{\odot}/{\rm yr}) and stellar mass ({\rmlog}_{10}(M_{*}/{\rm M}_{\odot}) ~eq 9.5) derived from the resolvedanalysis are in close ( <~ 0.3\,{\rm dex}) agreement with thoseobtained by fitting the integrated photometry. In contrast to studies oflower-mass sources, we thus find a reduced impact of outshining of the older(more massive) stellar populations in these normal z ~eq 5 galaxies. OurJWST analysis recovers bluer rest-frame UV slopes (\beta ~eq -2.1) andyounger ages (~eq 100\,{\rm Myr}) than archival values. We find that thedust continuum from ALMA-CRISTAL seen in two of these galaxies correlates, asexpected, with regions of redder rest-frame UV slopes and the SED-derivedA_{\rm V}, as well as the peak in the stellar mass map. We compute theresolved IRX-\beta relation, showing that the IRX is consistent with thelocal starburst attenuation curve and further demonstrating the presence of aninhomogeneous dust distribution within the galaxies. A comparison of theCRISTAL sources to those from the FirstLight zoom-in simulation of galaxieswith the same M_{*} and SFR reveals similar age and colour gradients,suggesting that major mergers may be important in the formation of clumpygalaxies at this epoch.